Sometimes it can be regional based. For example in the south we say "ya'll" but in some other places they say "you guys" (or yooos guys).

I feel awkward saying ya'll a lot so I use you guys. But many times the group I am referring to is female so I use you girls or ladies. This can get you in trouble depending on the age of the group sometimes I get: "are you calling us young/old" and then I go back to ya'll.