For PSP development, PPSSPP can be very good if configured correctly and you know how to use it.
You can debug on a PSP using psplink but compared to PPSSPP it's a nuisance to do it every single time. Plus, using a GUI debugger is way nicer anyway.
What really fascinated me was Sony's approach. For all intents and purposes, it was on par with the PS2 or even better (because of more memory).
Yeah sure, the VUs coupled with the GS throughput were better for graphics processing than the Media Engine in the PSP, but the devil is in the details.
But unlike the PS2, it has a real OS that is capable of loading modules and even do some fake multitasking! This was groundbreaking for the time and this is what made it so magical for homebrew IMO.