Ugh... I hate that I'm even going to state this but...
If DS had better graphics people who like Gameboy would use it as a reason that DS is better... but because PSP had better graphics the people who still want a DS will say Graphics are irrelevant. And yes, it works both ways.
So with that said, I've never been much of a fan of handhelds except before my Pokemon days. But PSP brings games to the table that I am interested it. MGS and Gran Turismo are two of my favorite games... if it has a decent version of Madden and a more classic Tony Hawk (THPS1-3 style), I would say by FAR it's better than DS. I don't care for the extra features all too much, but the game line up is jaw-dropping in my opinion.