TL;DR= As a homeowner who has used it for a few emergencies, My 18" bar CS400 has been outstanding in every way.
Full story below.
Not sure if this helps or hurts, but here we go...
I bought an 18" bar CS400 at 945pm in an HD running on backup generators because a storm with sustained 70mph straight line winds had just come through our area and the only thing I had to begin removal of the 6 storm felled trees (including the one across the driveway blocking my truck and the one laying on the house we bought a month before) was a 6lb axe and a bow saw.
A hasty purchase because we had no power and there were so many trees down around us, the power company would have been at least a week away from restoration. Since half the area had been cleaning HD out of the cheapest saws they had for about 2hrs before I arrived, this was the best saw still available in the store; I didn't have time to F around, so home it went. We cut with it through the night and next day, only stopping to refuel and sharpen the chain.
After shredding those 6 whole trees, 4 of which were approx. 60ft tall, I've used it for trimming and firewood. It's never failed, not even once. I'm also obnoxious with maintenance and run it at least once a month on the same day I run the generator, both for about 15mns for no other reason than to keep the party going and the oil flowing. I do this while mowing the lawn as to limit my noise pollution ;-)
I don't know how it would hold up to the rigors of daily use by a tree service/fire dept/circus juggler, but it's been great for me and I'll likely never by a new one, regardless of how much I eye-F the stihl ones at the local dealer.
If you get one, I hope it treats you as well as mine!