I have an old 290 workhorse for big stuff. Over the years, I swapped out the 20" "farm boss" bar for an 18" Oregon bar and chain and will never go back to the bigger bar. It cuts faster, runs longer, and is way easier on chains than the bigger bar/chain while sacrificing very little as far as maximum cut size. This saw is one of the best purchases I've ever made. It's 20 years old and still starts with 3 or 4 pulls every time.
When I wanted a smaller saw, I ended up going with the MS 194 T. The one-handed operation is a HUGE plus, and that little 14" bar is like a light saber. It punches way above its belt and can take down both the small stuff and some truly impressive feats. I've got a couple hundred hours on this saw at least, and other than regular maintenance its been a rock star.
I've had the best luck with Oregon replacement chains. They're cheaper and last longer than the Stihl branded units IME.