If your boat is of a certain length having an EPIRB is not optional. My neighbor's fishing boat did not meet the requirement so when I upgraded to an ACR ResQLink, he got my McMurdo. Personally, if I had a boat with enough length to require an EPIRB, I'd prolly have enough $$ to carry a PLB as a back-up. Maybe one on person, one in the life-raft.

I have this thing about floating around in cold water with no one having a clue there's a problem. Back-ups are a good thing, cheap insurance.