You have the key points, but another to consider is being able to pack it up if you aren't comfortable or otherwise don't want to leave your dingy dock/shore side while on the hook.
I use a tiny RU and would most certainly prefer RIB given the opportunity, but the dog and I have gone through pretty much any condition you can imagine just fine with the ol' softy.
Also a tip for RU, especially with K9 in tow. I put a couple of inexpensive, self inflating sleeping pads in the bottom. Gives you a bit more time with dry feet and more comfortable for the dog to stand without sinking into the cloth bottom.
Oh, and depending on the terrain you are landing on, might want to mount fold down wheels. I've actually been pretty impressed with the durability of mine (mine's made by a company called Plastimo), but it wouldn't last a year without major repair being dragged across the barnacles and rock around here. RIB will of course take more abuse being run into rock and whatever else might be just below the surface.