Ten pages into this thread, and Cedarkerf got it right!
"Since when someone says they have a 20" tree and I show up and it's any where from 12-32" in diameter I'd bring the saw that finally got me to stop missing my 10mm 044 Light enough for small stuff big enough for when they understate the tree size."
The size of the tree that your friend or neighbor calls you about is almost NEVER accurate...!
A few years ago I got a call that there was a 2 ft. tree blocking a popular trail. I was in the area, and had my old 056 Mag, with a 36" bar, in the truck, so I hiked in to cut it out. The tree was a big fir, just under 4 ft. diameter, and 4 feet above the trail - on very steep ground!
I was able to make 2 cuts and send a 6' section into the river 50 feet below!
Last weekend a friend and I went out to cut "9 trees across a trail, average diameter 15 inches"....... the biggest one was only 9"!
Take enough saw to handle most anything possible in the area!