Hi and welcome to FTR, good to have you here, thanks for delurking! Post some hands in the SNG forum, we don't bite there, I promise!
I've read somewhere that multitabling reduces your ROI by 6-8% but increases your hourly rate. I mostly just single table because a) I want to make sure that I don't miss any +EV pushes/calls and I'm not there yet and b) single-tabling allows me to deal with interruptions without getting timed out.