Two-color blocking buffer? BSA vs FBS - (Nov/29/2007 )

I'm starting up a round of dual color immunofluorescence assays and I was curious if .1% BSA or 2% FBS was the preferable choice for blocking. I've seen protocols using both types of pbs/azide staining solutions and I'm not sure if it would make a difference which one I chose. Does it matter typically?

Thanks.