It's rather difficult to brick a card flashing it. If it fails for some reason, you can generally just flash it again, and all is fine.
In theory the "FTW" should be better, but EVGA doesn't really bin their GPUs anymore, so it's hard to say. My ACX SC is worse than a majority of normal reference 780s probably. It does 1200mhz or so for gaming, which is plenty overkill for me, so I'm not really worried about mine.
Get them both, bin them, then keep the better of the two?