A lot depends on your comfort level with casting a sinking line. The full sink line with sink right up to your rod tip while a sink tip will not. If I was buying a sinking line JUST for fly fishing in the surf, it would be a sink tip rather than a full sinking line. SA, Rio, Airflo etc. all make sink tips in the fifteen to twenty four ft.length that would be very good in the surf. I'm basing my opinion on fishing the surf in Maine around Popham Beach for years. If your beach is very steep and deep, the full sink might be better.