Which line for a mainsheet

[Brion Toss]

Hello,
Apex is a fall-protection rope, and as such it will be too elastic for anything but a mooring line. Regatta Braid really is the best rope for your application, with the current configuration, but the same things that make it so, also make it vulnerable to snagging. It just doesn't do to say that the bolt heads are filed smooth so snagging is a mystery; something is grabbing those yarns, and it can be treated.
Another option is a 3:1/6:1 purchase made from 3/8" Sta-Set. This will run smoothly through the same size blocks, go out and come in 40% faster when you need that, and come in with 20% more power when you need that.
Fair leads,
Brion Toss