As a reminder, the PlayStation Portal, or Project Q, is (according to leaks) based on Android. It doesn't run the games itself, it merely streams them from your PS5 and your handheld then serves as a controller with its own display.
I'm wondering why anyone would prefer that over simply using a regular Android phone with a good controller and the PS Remote Play app?
Exactly. The big issue is the fact that it doesn't technically do any processing on-device and simply does streaming. So if this ever gets jailbroken, it will need to involve more than just software since you'd need something with a reasonably fast CPU to run that software.