hmm
well ive done both and the phat psp has a lot less tricky bits, no trigger springs etc
the psp i found was more about layers, the ds lite is all about sections, the top and the bottom
to do any testing while modding you gotta have the wifi bios chip plugged in and both screens, or none of them at all will work, but nothing in between.
having said that the ds lite is not particularly hard, no disassemblies really are, but at the same time if you dont do them right, keeping track of your every move like with any console it will make reassemblies a
in short keep track of the order and how everything was done, in particular the trigger spring positions and what you unplugged first such as the touch panel, this has a seperate connector you gotta be careful to remember how it went.
hope that helps