I picked up the Echo 58V last year to help clean up the land I bought. That thing is a little beast! My dad has a Stihl that's the same size. I haven't noticed any difference. But I'm not going after big trees or processing a crap ton of wood so YMMV. It goes through wood just fine. I've cut up a few trees that were a little smaller than the blade.
When you think about run time keep in mind that it's only killing the battery when it's running. Finger off the trigger and it's not running. So 4 hours of work you should still have plenty of power. You won't actually be running the chainsaw for the whole 4 hours. Again I only work with it a couple hours at a time but I don't think I've ever been lower than 3/4 charge.
It seems to be built well enough but mine started leaking chain oil from somewhere. I haven't tried to figure out why yet.
No gas... Quiet... Very little maintenance. Always ready to go...
I can charge it in my truck with the power inverter. Everything I need to run the chainsaw is always in my truck not stops anywhere.
I will still have my old Stilh (16 inch bar) and an even older McCullough with a 22 inch bar for the bigger stuff.
This would primarily be a truck/camp saw.
Years ago I had a little homelite chainsaw with a 12 inch blade for 4x4'ing, I never should have gotten rid of it