Going to assume you meant C hubs as opposed to the A and/or B hubs which are included with the kit. The C hubs make the rear rotate and square up more quickly, but you need high bite conditions or else your rear will be sliding out.

I have C hubs and access to a few high bite clay tracks in my area. I'm going to start with the A hubs, but I'm sure at some point I'll try the C's (used them at times on my 44.1). I'll post back on this.