None of these boats are able to be righted singlehanded in most conditions. You would need to purchase a righting pole or Gary's righting method. The righting bag in my opinion doesn't work too well.

I haven't sailed all of these options. They are all good boats though. I owned an 18-2 for a while and it was a great boat. However the 18-2 is the only boat on your list with centerboards but they do kickup. Also the 18-2 is a bit more fragile of a construction than the other boats. Thus the 18-2 performs a little better than the other boats so there are always tradeoffs.

I really like the SC17. I've never sailed it but have sailed against it and it is very fast. The 5.7 and P18 are both nice boats as well.

As long as the hulls are solid and it's in good shape you really can't go wrong with any of these boats.

Mike Hill
www.stlouiscats.com