Doing some quick comparisons for you. Numbers pulled from official Stihl comparison chart.
201 rear has the same power as the 211 so not worth switching to it. Great saws but you want more. Current 201 are mtronic. 35.2cc, 9lb head, 2.4/2.3hp.
Next up in power is the 251. 45.6cc, 11lbs, 3hp
Next is the 261 (mtronic is nice). Same power as the 291 but the weight of the 251. 50.2cc, 10.8lbs, 4.0hp
271 is 50.2, 12.3lbs, 3.5hp
291 is 55.5, 12.3lbs, 3.76hp
My dad has a 210, I have a 261cm. Wood hoarders thread convinced me.