I own both the PS2 and PSP version of the first Disgaea and I'd recommend the PSP version. Not just because of extra content, but the game looks real sharp on the PSP screen. Plus there isn't any slowdown that plagued the PSP version of FFT.

Disgaea as a game is still a bit overwelming for me. I got close to beating it on both the PS2 and PSP but never quite got there. Don't think I'd ever go back.