CLS.
Why? You have a CCB for Frosts. CLS is good for Bandos, the best (It's weak to slash). I also find CLS a lot more accurate in PVP situations. And for your KO in PVP situations you'd use maul.
If I remember correctly, CCB is just as fast as a rapier when both used with a cannon at frosts. As long as you stand next to the cannon and refill it when necessary, you should be able to get as much kills per hour. CCB would probably even get your more kills per hour with a yak, assuming you're using void.