My thinking is like so: Keep it on the PSP, with the same/similar set-up as before and it's
guaranteed to sell less in NA than Japan. At least if you offer a port of the game on another console that's NOT practically dead in the West, you have a chance of turning the tide.
Maybe it's not the best correlation to make, but I'll still throw it out there: Tekken 5: DR for PSP was a nice thing, but it wasn't until the up-scaled, PS3 PSN port came out (and then online soon afterward) that the game really started to catch on, especially in the West. And the reason why should be simple - a community-based game of that sort just was not going to fly until it had certain amenities that would best work for the game's purposes. Again, especially in the West.