I'm curious about OP's question, as well.
Speaking strictly from a grab 'n go perspective, I've sometimes grabbed my QSC K-10 for a specific gig, because i know that I can plug a vocal mic into 1 channel, set to "Mic" instead of "Line", and sing, do vox announcements, etc. If I know I WON'T need any vox mic use, I'll grab my CLR Neo, because it sounds better for guitar/AxeFx.
Speaking as one who's so far been too lazy to try it out... would a vocal mic straight into Ch2 of the CLR produce a reasonable mic level, if the input gain was maxed, given that there's presumably no mic preamp in it?