Both devices have the same resolution cameras, but the 3DS has three cameras (giving it the ability to take 3D pictures) while the Vita has 2 (which leaves it permanently stuck with only 2D). Even though it's a quality few care about, the fact is, it's still better.
As for portability, you're crazy if you think the PSV has anywhere NEAR the same level of portability as a 3DS. Let me demonstrate with a slightly old picture:

and if that's not obvious enough:

SW-5120-1900-6153








