I live in the Great Lakes. The water level goes up and down everywhere over time. Even here where there are no tides. In general, I believe floating are best, but not the cheap ones. The most expensive solution unfortunately.
Fixed must be used where there is a lot of wave action. Floating can always be used in backwaters. The ones with concrete pads on the top are the nicest I've seen. A great $$ saver is to use fixed center docks and floating fingers.