I would say volt edge for more damage, assuming you don't need extra space by immobilizing zombies.
But I would recommend DA over brandish on FSC.

Personally I prefer Voltedge for the extra damage, since the Glacius' statue only does damage when the zombies naturally thaw out, which doesn't happen often in parties or when you want to spam charge attacks. Glacius is better with crowd control in a pinch, though shock stops zombie lunges sometimes as well. You should also consider if you're willing to grind out a bunch of PvP games for the Volt line's recipes.

I hardly ever use the glacius. I find freezing stops me from bumping zombies and offers no extra damage. Note you cannot shield bump a frozen slag out of the way, which I find useful from time to time, especially if you need to make an escape route.

I prefer my combuster, even though the fire offers no advantage for fsc. It lets slags take full damage by riding the full charge wave. Since I really only use the combuster, I've gotten used to predicting where the slags will go and have worked out a sort of system.

I have used a voltedge in the test server. I found it annoying since it stopped me from lining up the slags in the ways I am used to, and it has less damage since the shock status stops the slag from getting hit from a full wave of the charge. A poorly timed shock status on a slag could stop a shield bump if you needed it. IF you like shock and having them clump, then use the voltedge.