According to Twitchfilm, each version would have both dubbed and subtitled dialogue using the character names from that region's version of the games. So Miles Edgeworth, et al. in America, but ... Benjamin Hunter in France.
Now that we have admissible evidence that we'll be able to see the movie, how is it? "This is definitely a love-it or hate-it affair, and if you don't dig the silly caricature tongue-in-cheek atmosphere which inhabits the universe of 'Ace Attorney,' you will tire of the film way before its halfway point has been reached," Twitchfilm said. "But if you DO have fun with it, this is the fastest way to spend almost two and a half hours."