@Hclegend 
Well, even if you say their powers are from geodes, Sci-Twi has powers more akin to an unicorn (ie telekinesis/levitation of objects) akin to an unicorn, not pegasus (again, multiple unicorns shown powers to levitate objects).
 
And Sci-Twi started to have arguably magic even before contect with geodes - as her nightmares with Midnights might indicate. It’s also notable Twilight awakened first her powers, and seemingly induced them in at least few others, including pony-up transformation: 

 
Showing she at least has a greater ability to absorb the magic of geodes, and share it - something very unique, and more akin to and unicorns and alicorns (ie how Pony Twilight awakened magic in others in the human world), than anything else.

@ChuymaruZ 
Drama’s fun until you get banned for Rule 0.
 
Despite the other person clearly breaking the rule too, you reporting it and being completely ignored because you’re banned and the offending comment only getting removed when someone else reports it, implying that it did break the rule like you suspected, but was ignored due to you being banned.

@Zharkaer 
I know… its not the same… I miss the drama in the comments tag

@BackgroundLoL 
Again, magic. Sunset becomes a mind reader. Not to mention the fact that the power comes from her Power Rangers Necklace Thingy, not from her inherent magic. It’s possible it was Pony Twilight’s magic, for sure (It’s PURPLE.) and while something I forgot she had, can easily be disproved by the fact that again, Power Rangers Magic Necklace Thingies. Sunset could have gotten pyrookinesis and nobody would have batted an eye. The fact that the necklaces thingies also give similar powers to their respective bearers (Dash gets speed/flight, AJ gets strength, Fluttershy gets… Animal communication?) backs this up.
 
 
@Zharkaer 
Justice Rains From Above?
 
eh, it’s a booru site. More here for the pretty pictures than the discussion. Hence the Matpat level of ass-pulling.

@BackgroundLoL 
Just wish there were less additions to the discussion in the comments tag.

@Zharkaer 
Dunno if the situation here is that bad. I saw many much more toxic threads under pictures, and in forums…

Kinda wishing the comments could be nuked

@Hclegend  
Again, Sci-Twi uses magic in a visibly unicorn-like way (ie telekinesis/levitation of other objects), can induce magical transformations in others, and as Midnight, would destroy the (human) universe (or at the very least, world) via portals that errode reality.
 
So I think Sci-Twi would be an alicorn in Equestria.
 
(to be clear, Midnight is a different personality, and seemed to drunk on magic to fully understand what she’s doing).
 
Again, I don’t think Sunse is an alicorn, but could be one, just subconciously, or conciusly stopped herself from becoming so with guilt, and greater self control of magic than Sci-Twi.
 
 
@BackgroundLoL  

 
So my theory does take into consideration why Sunset is an unicorn in Mirror Magic, and I never denied it, as I think Sunset still is an unicorn, but could becoe an alicorn, if she really wanted/needed it…(and fully got over her guilt over her Alicorn desire motivating her to do bad things…)
 
Although to be fair, Midnight Sparkle, was also visibly stronger than Daydream Shimmer - indeed, as some noted, Midnight is kinda the Broly of MLP. Even more of an invicible antagonist, seeing it’s allways kinda Sci-Twi who defeats Midnight (from within), if with Sunset’s emotional support.
 
(to be clear, both times Broly was defeated in movies, it was witha plot device of sorts - via Goku’s sudden power-up from the Z Warriors, and by Goku being semi-resurrected, or giving enough emotional motivation for Gohan and Goten to give them a power-up, like against Cell. Also, the second time, Broly didn’t fight exactly seriously, and was distracted by Trunks..)
 
[EDIT]
 
Well, Broly was defeated three times in movies, if count Bio-Broly (who is a failed clone of Broly, rather than the reall thing, but still…), but even Bio-Broly, was defeated by an plot-device, via his weakness to water.

@BackgroundLoL 
More crystal than metal, but sure.
 
But there’s one itty bitty thing… That only proves that she could be a pegasus if she visited Equestria. Not explicitly an alicorn. Sure, her pony counterpart is an alicorn, but that proves nothing. After all, it’s a seperate universe from the pony world, where magic did not exist and the Humane 5 all ponied up based on Twilight’s Equestrian magic, so obviously they’d resemble their pony counterparts more**. SciTwi wasn’t exposed to the same magic until she was consumed by the giant ball of magic that turned her into Midnight Sparkle, who’s wings are distinctly feathered, much unlike Sunset’s fire/ethereal wings and horn. Note how Midnight’s “horn” is also very much ethereal.
 
This could imply that in fact, she absorbed more pegasus* magic than anything else, doubly justified by the fact that there’s ONE unicorn in the Humane 5 and two pegasi/earth ponies, permanently making her a human/pegasus hybrid, ala Rainbow Dash and Fluttershy.
 
And since it’s all magic and science, it cannot be disproved without seeing her physical pony form within the show, much like how Sunset is STILL an unicorn in Mirror Magic, despite absorbing a similar amount of magic as SciTwi did.
 
TL:DR SciTwi is a pegasus.
 
*That and they’re carbon copies of their pony selves anyway, while SciTwi has had a different upbringing compared to PonyTwi.

@Philweasel 
@Philweasel
 
Also, I’m not sure if Sci-Twi just “borrowed” Twilight power-up, or wings, because as Midnight Sparkle, she would errode the whole world, possibly reality (seeing how this thing works), with her portals, showing far more power than anything else in the franchise.
 
Yes, she absorbed magic with her device, but all latent magic released during the first three movies, or a lot of it, not just that released by pony Twilight, which is why I think there is the share power difference.

@Hclegend  
There is A LOT of instances of Sci-Twi having alicorn wings - she had them through a visible part of Legend of Everfree, as shown by Zharkaer.
 
[EDIT]
 
Another instance of it:  

 
So everytime Sci-Twi goes Pony up, she get’s wings. When she goes super pony up, she get’s metalic wings, but so do Fluttershy and Rainbow Dash:  
>>1361029p (merged)

@Zharkaer  
Cut me some slack, haven’t seen Power Rangers since it released. At least I know now. could easily be a pegasus fight me
 
@Philweasel  
… i prefer my theory.

@Hclegend  
She exploded a ball of harmony in her face, which turned her into an anime supervillain.
 
Power which I note was originally from Twilight Sparkles magic power up from the first movie.

@Hclegend 

@BackgroundLoL 
Considering that’s a music video, that’s very debatable. Especially as there’s no other instance of it.
 
@Philweasel 
Sounds gruesome. Did she need a hacksaw or what?

@BackgroundLoL 
@Philweasel 
I would say it’s at least five and a half

@BackgroundLoL 
I personally believe SciTwi is borrowing PonyTwi’s wings. She’s still a normal human after all, just with Equestrian magic fused to her.

@Hclegend  
But Sci-Twi is an Alicorn - she has wings and unicorn magic in her pony-up form:  

 
Also, indeed with Flurry Heart and Sci-Twi, we have 6 Alicorns XD
 
[EDIT]
 
Also, my theory with Sunset, is that she isn’t a alicorn after becoming Daydream Shimmer, as she mentally denies herself being one - out of guilt how dreaming of being an alicorn, caused her conflicy with Celestia, and in large part the bad things she done in the first movie, and before.
 
As Sunset has greater control of her magic, even subconciously, than Sci-Twi (who never used magic before), this is possible, I think.

Oh wow, caused quite the mess here, didn’t I?
 
 
@Zharkaer 
Emphasizing words is fun!
 
 
@BackgroundLoL 
That’s a completely different scenario, though. It’s like saying the Mane 6 should be alicorns because they’re the Elements of Harmony. (Also the alicorn thing in Daydream Shimmer/Midnight Sparkle? The amulet thing had unicorn and pegasus magic inside of it. It doesn’t mean that they’re bloody alicorns.)
 
 
@Silent Wing 
Flurry Heart. Also check the picture above that started this debacle. Shimmercorn!… still not canon, thanks mirror magic!
 
 
@Josh103 
Cadance eventually got a purpose and Twilicorn was thoroughly earned by saving the world… 4 times at that point? Along with gradually becoming a beacon of friendship. Also they managed to work it well during Season 4, something that Shimmercorn won’t be able to do unless she is either forced into the show itself, or EqG becomes it’s own series.
 
Oh right and Sunset is clearly more comfortable in the human world, so this idea of her returning to Equestria at all, let alone as part of the master race, is ludicrous and stupid. Let’s not even get into SciTwilicorn, otherwise I’ll be here all day.
 
Still don’t agree on any more alicorns. Flurry Heart was very much forced, and Starlight/Sunset/Scitwi aren’t worthy of it. Not their own faults, mind. There’s just the distinct possibility of absolutely massive backlash. Imagine Twilicorn, multiplied by Starlight drama. Yeah… That’ll be a real Base Breaker.

Unless that alicorn we saw in The Book in hearts and Hooves day was cadence then there are technically 6 alicorns

@Silent Wing 
Sci-Twi

@Silent Wing  
…Flurry Heart, dude, calm down.

@Hclegend 
Considering how there didn’t need to be any more than two alicorns and that was thrown out the window years ago, I’d say they go for it and make Sunset and Starlight alicorns too why the heck not.

@Hclegend 
>5 alicorns 
Where this 5th one I’m hearing about? Am I missing something?
 
>inb4 Sunset Shimmer is an Alicorn 
NO.

@Hclegend  
Well, it’s not unrealistic for Sunset to become an alicorn - she became Daydream Shimmer by the same magic, that turned Sci-Twi into an alicorn.  
But to be clear, I’m myself not sure if Sunset will become an alicorn.