Sony PSP or Nintendo DS Lite,pound for pound which is the better portable handheld gaming system?

I'm buying either of these very soon...I want a gaming system with excellent graphics,gameplay and a variety of games suitable for adults and teens(and some kids games too)..ability to do other stuff would be cool as well...I was more leaning towards buying the PSP 2000(not 3000) over the DS lite...good idea or not?