RE: DS3301 or DS168
DS168 is about 1/2 the width give or take. I would use it only if I needed the narrow width. In my experience those crazy narrow servos have weaker gears but maybe the 168 is different, I don't know.
I have used the DS3301 on several occasions and I like it a lot. I think it is spec'd on the BobCat for rudder.