The crossover of dreams satisfies, if not satiates
As a huge fan of the Ace Attorney series and having been charmed by Professor Layton and the Curious Village (in its EU incarnation), I'd been looking forward to this crossover since its first announcement.
Since both games are essentially visual novels, the two styles pretty much seamlessly blend into one another: the story is divided into chapters and the world explored Layton-style, with some of those chapters involving trials played Wright-style. This doesn't mean Nick doesn't get to solve puzzles, nor does it mean Layton doesn't find himself in court--on the contrary, these things do happen--but it's very clear-cut which bits come from which franchise.
The interface is a blend of both, and elements of one creep into the other--most notably, you can use hint coins during trials to figure out your next action. The original spins are much more biased towards AA: while the Layton puzzles get a bit of a medieval slant due to its settings, AA gets group testimonies, in which you can cross-examine a handful of witnesses at once--and pressing a witness may cause contradictions to arise in someone else's testimony, or may cause someone else to react. The designers get some creative mileage out of this, but it only feels marginally different from the other AA gameplay mechanics thrown in over the years.
The setting itself is very Laytonesque, which makes sense, but the characters are pure Ace Attorney. The former makes sense as "a city that is a puzzle unto itself" is probably easier to resolve than the puzzle that is where Phoenix Wright and Maya Fey live (is it Tokyo or a ridiculously Japanese Los Angeles?), and the latter brings forth some memorably outsized personalities. Most notable is one character who doesn't even get a name for some time after his entrance (he's labeled "Some Guy" for most of the trial he serves in), with the reveal of his name serving as a punchline of sorts. While the traditional AA rogue's gallery is missing for the most part, these characters do an admirable job of filling in.
The plot serves its purpose in uniting Wright and Layton (and their respective seconds) together, and while the plot takes a while to get momentum, once it does, it starts really steamrolling. You can play strictly for plot, but you'd be missing out on all the puzzles that are at your disposal--exploring and hearing the observations of your player party easily doubles playing time. However, I wouldn't blame you for wanting to see what unfolds next and solving everything else later.
If you like either franchise, you'll most likely enjoy this game. At a price that's lower than other 3DS games, it's worth a go.