I own a PSP with custom firmware (m33 v3.80).
I have a 4GB filled with games from different systems and consoles (NES, SNES, Master System, Arcade, Homebrew, . . .), including PS1 game ISOs
Original games I own: Metal Gar Ac!d 1 & 2, Metal Gear Solid: Portable OPS Plus, Final Fantasy Tactics TWOTL, Ape Escape: On the Loose, LocoRoco, Crash Tag Team Racing.
I don't think PSP is better than NDS, both are two different consoles with pros and cons.