At the moment sky3ds and GW both have advantages and disadvantages over the other, so it's kinda hard to choose.
Basically this. I have had a gateway for a very long time now and loved it every step of the way, but if my Majora's Mask N3DS isn't supported by Gateway tough luck, I'm going to get a SKY. While I do have faith that they will follow through with their promises I don't expect them to magically support >9.2. If Sky does not support New 3DS exclusive games I'll wait until some flashcart does and get that instead, otherwise there would be no point.
Current Benefits of Sky:
Sky works on all current Sysnand Versions and N3DS
Partial Region Free Support thanks to Smealum (?)
After the initial blunder, not limited to just 10 games ever
Easier for people with children than Gateway (More straightforward use)
Downsides of Sky:
No homebrew (AFAIK)
No Emunand
No CIAs
May get blocked out in an update
*Not Officially on my list* Takes ages to switch ROMs when you have a bunch
Current Benefits of Gateway:
Support all the way to 9.2
Downgrading sysnand (Can even be used without owning a Gateway)
Restoring NAND
Emunand
Homebrew
CIAs
Active development with more features promised in the future
*Not Officially on my list* Has opened up the way for CFW and more exploits in the future, their new launch method has already expanded the scene in promising ways
Current Downsides of Gateway:
The updates aren't magically instant, and not all promised features are currently supported, although this could change at any point
- Cheats (Pls no)
- New 3DS Support (Not public)
- GBA support
Does not work above 9.2
Possibly still contains Brick Code
Really bad support and communication with customers
Only Reason MT-Card is allowed to Exist:
Their Emunand isn't locked to owners of the card itself