Not at all. Sky3DS and Gateway are very different.
If you want to use a N3DS, as things are now, Sky3DS is a better option (because really, getting ZeldaOOT or Cubic Ninja and using it every time is a PITA).
But for an old 3DS with FW 9.2 or below GW is a better option.
If using out of region games is important for you, for example. I use a lot of japanese games, it is important for me.
And good luck playing eshop only games like Phoenix Wright Dual Destinies in your Sky3DS.
Also the possibility to install CIAs and remove the card makes it way better, the battery lasts a lot longer.
Thanks for clearing that up out of region is a big plus...I myself am dieing to play river city rampage on the 3ds so I might look into gateway as well.