I've done well at both on the dock, half moon harbor has an excellent pier on winchester bay and the south spit at yaquina bay does pretty well at the dock there.A word of caution... a few years ago a crab pinched a lefty and now they are all infested with blue tumors. Highly toxic!!
If you like living on the edge... with a boat, Winchester Bay is highly productive. Dock crabbing... further North in Yaquina bay off the marina pier is generally okay if you pay attention to the tides. A boat there is still a better option, but if you have a boat... Winchester is your best bet.
If you're farther north, Nehalem Bay has two marinas on the south side just off HWY101 owned by the same family. About $15 a day; ring and cooking included, and if you don't have a boat they'll rent you one!
Nehalem Bay crab are superior to all except the crab past the bar and still might taste better!