What about kickboxer v Karate?
It would all come down to the individuals in the fight, One style generally is not better than the other, but all styles have their strengths and weakness' Thats why there is huge momentum in Mixed martial arts.
Learning different styles really helps to enhance you fighting abilities.
Boxer vs kickboxer karate etc, all things equall I would put money on the guy that has more weapons,... the kickboxer, the boxer tends to be very vulnerable in the legs as he hasnt conditioned them to be mashed by thigh kicks. You may not get in is guard but the house will come down once the supports are trashed, legs also have a much greater range at leg and mid section height.
Kickboxer vs karate, thats a tough one but again the kick boxer is more conditioned to the bigger hits, and once you get some one in a grapple you can inflict big damage and lots of nasty close hits, elbows knees head buts, etc,
I Have trained in Karate, and the club would do kickboxing nights, go to the local boxing club for a few weeks and swap training ideas, we also had a few jujitsu lessons, but the same club also did muay tai kickboxing. There is so much more emphisis on power, and the techniques are very different, I have also done a bit of Tae kwon do mainly because I loved the legs stuff, Again quite different, and more challenging technique wise.
So I am a mixed bag really, I also went to a few kung foo classes also with a mate, and hated it, or maybe just how it was taught.
As mentioned in the end it comes down to who is better at their chosen style, and how bad they want it, and never underestimate fitness I have seen it win lots of fights.