Floating docks are generally safer if your water level goes up and down a lot, but if the water level stays pretty much the same year round where you are going to use this pier then I think a permenant structure would actually be safer: Permenant structures should be a little more stable. I've seen floating docks that were so poorly built that they would move around under your feet so much that they are not really safe to walk on.
Of course a poorly built permenant dock would also be unsafe so make sure you do it right!
