I would go with a stihl ms362 if you are going brand new. if you are willing to go used then a 361 or nice used 362 should last you for a long time. I wouldn't go any smaller personally. I personally I ran my ms440 with a 25" bar for a day and it was a beast. I haven't taken the 28" bar off in a year now, and the saw runs pretty good with that on there. I would go with a ms660 but i can't find a good used one, and new one is about 1200 with a 36" bar. you are always gonna want a bigger saw, so I would go with a ms362 if you are really concerned with weight and power. but personally I would go with a ms440 or 460, and you will love it with a 20" bar it will cut through everything with ease....
fully lic. and ins. 10yrs exp.