Im considering switching to BTC Guild from another pool, but I am still new.
Do most miners in this pool use CGminer? If so, why? Why not BFGminer?
I am currently using BFGminer and it works well. I have BFL equipment.
I personally recommend bfgminer over cgminer for ASIC users, but both are in the recommended clients. I've switched my preference back and forth over the last year, but in general I prefer bfgminer for ASICs.
I don't know for sure what the split is, but I'd bet it's fairly even between bfgminer and cgminer.