I had a similar problem where the window would stop at certain points and I'd hear a clicking noise, I could help it all the way up by hand. I changed both the regulator and motor and now it's perfect again, took only 30-40 minutes to swap out.
S1 and S2 are only different in regards the switch loom plug and the S2 (and S1.5 I think) won't have the relay that S1 owners talk about repairing.