##778 is very limited on the HTC Hero Alltel rom, it has no options for changing anything, on the Eris, it's wide open, there's TONS of menus for changing absolutely everything and opening different PRL files, changing HDR authentication keys, etc... absolutely eliminating the need for using a computer to flash/reprogram the phone to a different carrier.
EDIT:
Here soon I'll probably root the hero and pull the telephony.db from the android OS, and throw it on my guinea pig motorola droid I've got coming, my ERIS is unrootable because my boot rom is the newest one that hasn't been rooted yet, lame, anyhoo, I'll let ya'll know if it works, if it does, I'll go through the telephony.db file and see what kind of sensitive info is in there that makes it work.