In terms of power the Vita just blows the 3DS out of the sky, in general its around 3-4 times faster and thats without factoring the 3D performance hit in. The Vita can run Anvil Next, I doubt the 3DS can even run the Anvil engine. And finally it has two analogue sticks, the Vita in general just has too many advantages for a AC game over the 3DS.
An AC game was announced for the 3DS but was turned into the console Revelations instead soon after.










