PSP is the best. But I have to say, I'll go with Nintendo on durability. The PSP has so many structure flaws. I got one the day they came out. I haven't bought another in a long time, so I'm going to guess they may have taken care of the screen and analog stick.
DS and gameboy advance. Why gameboy advance you ask? Because all of the amazing classic games that it has like super mario 3, all of the sweet pokemon games, zelda, and many, many more.