That might seem an odd thing to ask given we're still months away from the game's release, but thanks to the fact Ubisoft showed the same level at E3 on the two consoles, we can actually get a good (if early, and imperfect) look at how the Wii U is shaping up as far as multiplatform titles go.
And...well, call it personal preference if you like, but the Wii U version wins this one for me, mostly due to the improved lighting. At least, it looks like it. Though, you know, you'd expect that, given the console it's up against was released in 2006.
Of course, things can change between now and the game's release. And you can argue that the PS3's footage simply isn't up to the standard of that captured for the Wii U. And at the end of the day, it doesn't really matter, as the game will still be (mostly) the same under the hood (Wii U controller additions aside, of course).
You can check them out below. The Wii U is on the left, PS3 on the right (if you click the "YouTube Doubler" link underneath you'll be able to see both demos running side-by-side).
UPDATE - To those getting upset over this, relax! This is the first chance we've had to directly compare games running on the system like this. The PS3 footage may not be perfect, but I thought it was still interesting to compare!