I have owned and run an MS260 (sold and regret) and MS261. I liked the MS260 a little better just because it had the standard carb. My MS261 also sometimes vapor-locks when it is very hot and humid, but apparently this very rare with these saws, so take that with a grain of salt. The HD air filter on the MS261 is much nicer. So I guess I'm saying that there is no clear winner. Both are very similar in performance.
I see your old one is up for sale. I like it. Haven't seen the lightweight version here yet. There's no power difference from what I've heard between the oe & lw. 026 vs 261? I'll take the 261. The power difference is definitely noticable.