My MS250 has the 18" bar. Most 80%+ of what I use it for likely could be handled with the MS170, but nice to have some reserve for bigger trees now & then. The MS250 is light and handles well for me, I don't mind the little extra weight on smaller brush & limb stuff.
My favorite chain on this is the RSC (Rapid Super Comfort, yellow label) It is a smooth fast cutter.
