Pepcid AC is an H-2 blocker like Zantac. Prilosec, is a newer generation of acid blockers called PPI's (protein pump inhibitors) that literally shut down most acid production. Prilosec is OTC but you can others like Nexium with a prescription.
As long as your doctor gave you a choice, I'd say go with the H-2 pump if it works.
If it stops working, then step up to either switch to Prilosec (or discuss with doc using in combination), or ask your doc for an Rx for another PPI like Nexium, Aciphex, etc. Both choices will not interfere with your riba absorption, like an antacid (tums, maalox, etc) potentially could. BTW Pepcid Complete contains an antacid, so probably best to avoid and stay with Max Strength Pepsid.
I tried OTC Pepsid on tx as well as Zantac, Nexium an Aciphex. I ended up on double Nexium for most of treatment but I had a really bad case of esophageal GERD called LPR. Now, I only occasionally take something like Pepsid Complete -- the one with the antacid -- but now that I'm not on riba (thankfully) no problema.
Glad the Pepsid is working for you.
All the best,