Gateway is cheaper though. On top of that you get emunand. That's a big plus. Sky I see for around 70-100$. GW I have seen 60$-80$. Usually not more.
Loading roms is WAYYYYYYYYYYYYYYYYY easier on Gateway. Press select then you have all your roms there. To add more just drag and drop on the microsd card. Sky I feel isn't as simple, while gateway is and also convenient. I'd go with gateway also due to the fact you can downgrade. The main homebrew someone would sacrifice user convenience for is DevMenu (ie. BigBlueMenu) for install .cia files and so on. GW is not inconvenient to me. I feel a lot of people may be angry about the online exploit, but the online exploit was probably so we could downgrade and use a fully offline exploit. On top of that, there is still ways to do the online exploit offline. Gateway also overall is better in terms of hardware upgrade ability. I have a feeling sky3ds will come out with new cards over time if it is patched, just like they had a red version and a blue version. Gateway has use the same card all this time. No one has had to buy a new card for the 9.2 update either. Though they may be slow, they came through and I have to give them that. Sky also has a 30 game limit that has yet to be fixed on the bluecard. I think gateway is less sketchier than Sky. My 2 cents though. Sorry I am late, hope I am not necro posting