PRG0 and PRG1 were chips on the NES carts.

That's the only difference AFAIK.
The exact same game with different chips.

 

Hi ,

I'm sorry to say that PRG0 and PRG1 are not 2 different chips you meant PRG and CHR.

It really stands for program 0 and program 1.

One slight difference between the 2 roms is the text appearing when you die "HOLD RESET WHILE YOU TURN POWER OFF"
This text is not present in one of the roms.

Difference usually is bug fixed versions of the game. So some bugs that were in PRG0 rom might not be there in PRG1 rom. The game itself will be identical.

Some games like donkey kong country for snes have many revisions. Or Star Wars for n64.

Edit:
I just wanted to add that Perfect Dark for n64 had a nasty bug which would block you from doing a certain star mission playing 4 people with Elvis. I don't remember exactly , but that was fixed in a new PD revision