Where I play, CTF is pretty much "ignore the flags" and "let's kill each other". Everyone treats it like DM without the 10-kill restriction.

If CTF is taken seriously, then yes rhinos are good at it. But i suspect that foxes are even better because they can actually kill players while leaping out of range. It's very useful to murder one or two birds before going on your way. I haven't really experienced proper CTF.