Friday-Saturday sounds nice. Still easy to catch up with friends - and I'd probably arrange more events on Friday knowing that I wouldn't be tired after work on a Friday - but having a free weekday would be nice occasionally, to see the sites that are only open during the week or aren't open as long on the weekends, as well as to take care of any errands to places with mediocre hours. Sunday-Monday wouldn't be as good since I rarely have social events on those days, and it would thus likely result in me socializing less.
Instinctively I think two days in a row is nice, and it does make road trips a bit easier, but I rarely do more than a day trip anyway. But I wonder if having, say, Wednesday-Saturday might work well? I tend to stay up late on the weekends and be tired Monday, but with only one day off in a row, I wouldn't get as far off on the weekend, and having two separate days out of seven off would mean a day off was never more than three days away, which could be nice. I wouldn't sign up for it permanently, but if I could try it for, say, two months, it would be interesting to see how I liked it.
But the current Saturday-Sunday isn't too bad either.