I'd guess the way I'd handle this is to advertise: GTA4! Coming to a PC or xbox360 (or whatever) near you! (and in slightly smaller print) Also! Next month! GTA:SAS for your PoopStationPortable!
that way, a good portion of your market, who has the proper console/video card, goes out right away to get the hugest, realest GTA experience ever. but everybody KNOWS about the PSP version, and people who HAVE a PSP might wait and just get the PSP version, but if they'd do that, they probably wouldn't have bought GTA4 anyway. Anybody who's a fan would want GTA4. The worst idea would be to release the cheaper PSP game first, have 100,000 people buy it, and then be so busy with it they don't care about GTA4. ^^;
i can't believe how good these PSP games are getting. this is a lot better than Ridge Racer. I might be owning a PSP sometime.