Reptile Relief will give your animal immediate relief, but it will not prevent eggs from hatching, and mites will return in about a 30 day cycle.
PAM completely erradicates mites. I've only ever used the two in conjunction when I rescued three ball pythons who were infested with mites and I wanted to kill the mites on them, but I put my money on the PAM to erradicate them. One treatment of PAM and I didn't have to re-treat.
I pre-treat the enclosure of all new additions with PAM, and I re-treat the enclosures of my existing colony when I bring in new additions to make sure I don't inadvertantly transfer eggs from one animal to another, despite my strict quarantine procedures.
I figure you can never be TOO safe with your collection.
PAM also goes with me when I travel to shows, and travel tubs for any new acquisitions are also pre-treated.