Older models are best, avoid the M-tronic Stihls and Auto tune Varnas. Seize tronic and Auto seize are more apt names. Adjustable carbs are the way to go, Walbro over Zama too, (but can't always get past the Zama thing). MS 460 /046 is an awesome saw with more than enough power for 2' trees. MS660/066 too, tons more power but getting up there weight wise. MS340/360/034/036 are good too. I own all these models and they get lots of use. In Varna if you can find one, 266 268 are tough workhorses. I would avoid the 3 series, weak fickle and prone to lots of parts breaking. (Mounts, throttle cables, stop switches, cover screws hog out with vibration, mufflers crack weak crankcases).
Opinions are like A-holes, we all have one, but mine is based on 40 plus years of saw service and repair. Still working in the same industry so current with the new models and their problems.