PSP games are way superior to DS games, the trouble is there aren't as many good games on PSP, there are loads on DS.
I wouldn't advise getting rid of your old DS for a new one.
The new screen is great, as are the DS pad and buttons, but the cartidge sticking out half way is very annoying, and some idiot decided the microphone should be above the screen instead of below. So unless you have eyes in your chin, you won't be able to play games that use this feature so easily.
Out of preference I don't know which is better, probably the DS lite, but to sell your old DS for a new one? That's just a bit of waste of money to me. I'm sticking with my old DS.
I wouldn't advise getting rid of your old DS for a new one.
The new screen is great, as are the DS pad and buttons, but the cartidge sticking out half way is very annoying, and some idiot decided the microphone should be above the screen instead of below. So unless you have eyes in your chin, you won't be able to play games that use this feature so easily.
Out of preference I don't know which is better, probably the DS lite, but to sell your old DS for a new one? That's just a bit of waste of money to me. I'm sticking with my old DS.