This question has come up before and lots of answers. The pros of a Fri-Sat comp is getting to stay the night after awards on Sat, driving back at your leisure, and having a day to recoup and put things away. Sat-Sun competitions may require you to drive home right after awards and then deal with putting things away, with no time for R&R. As some one who's done it, that can be a long drive and miserable Monday morning. I've always had a (not so secret) theory that Fri-Sat competitions are more common because they don't interfere with church, but what do I know?
A lot of ppl like Fri-Sat comps because it's what they're used to. They'll tell you, like I just did, that you have more time to recover, but you don't have to drive back Sunday night after a Sat-Sun contest. You can always take Monday off. Sat-Sun gives you the option of a 2 or 3 day weekend, whereas Fri-Sat does not.
That's my take on the matter...