Chowder or hard clams have a much higher iodine content. Their flesh is much darker than surf clams. When you shuck thousands of surf clams at the same time the room almost smells like the surf on a cool morning. Chowders dont.
Fresh or frozen it's always surf first for me. Also chowders are not found in or near the surf.
Started some serious efforts last fall with surf clams in the containers.could of been fresh frozen, salted frozen, fresh not frozen. Had a hell of a time keeping the bait onth hook. Used rubber bands,that little spool of stretchy string that all shops have sitting on the counter. Still had trouble,keeping the clam on the hook.Bought some fresh yesterday and after a few cast i had to comment on how well the clam stayed on the hook.Iced down what was left over and am getting ready to go catch high tide some place in C>M> county.Whatever is left over i will clean and salt to see how they work. If i didn't have to work tomorrow I'd keep them on ice as long as possible.I asked on another thread yesterday about keeping fresh and got back several good answers about storing them.And like Fred said when you shuck them they smell like the surf. Hope i have something to report in a few hours. Don