The rooms are the exact same other than some minor color differences. As for the hotel, there are a few differences, but they may not have much of an impact on your trip. Dockside is much bigger and has two smaller pools rather than the one large one that Surfside has. Personally, I prefer Surfside's pool but that is because I like the design of it.
I also thought that Dockside had some better food offerings, although it still the same cafeteria-type options. They also had a small lobby bar, which Surfside did not.
All in all though, I don't think you can go wrong with either property.