Why does this matter? Because the gameplay philosophy is entirely different.
Since the PSP can run certain Java emulators (like PSPKVM), some users package the mobile .JAR file to run on the PSP. The Experience: Sonic Unleashed Psp Rom
If you own a hacked PS Vita, Adrenaline runs the PSP firmware natively. Copy the into the ux0:pspemu/ISO/ folder. This is the best legal-like option because the Vita has real PSP silicon. Why does this matter