For example, take this panel down here:

Yeah, so if you're on a deserted island, which one would you choose as a companion?
The first one can give you blowjobs, handjobs, titty-fuck and quite possibly, conversation. But can never give you anal.
The second one can give normal sex and anal, but is disgusting. I imagine, for the second one, you have to put the top end in the water and doggy-style all the way.