Psion
Adventurer
I think that a few one book is all you need to get started RPGs (Traveller D20 and Spycraft 2.0, for example) are pretty nice.
That said...
2 and 4 directly contradict 1. Players don't need the material in the MM and DMG, so they save that much money, and that's a majority of the group.
That said...
Imaro said:Some advantages I see to the single corebook...
1.) Cheaper to get into.
2.) If you buy the book you now have the rules to both play and run the game(might facilitate more people at least considering trying to run a game.)
3.)Portability greatly increases.
4.)Better understanding of both player and DM perspectives and issues concerning gameplay on both sides of the screen.
2 and 4 directly contradict 1. Players don't need the material in the MM and DMG, so they save that much money, and that's a majority of the group.