Three for echo. Interesting. I only ever used an echo battery saw. Never heard of the 4310, never used a 261 either. The stihl looks pretty close on paper, 4310 looks very light weight.
I have a yard sale 2156 I was putting together for this but I expect I am going to find it a heavy old thing on longer treks on foot or ski.
That 2511t looks cute and handy, maybe a tad small?
The Echo CS 4310 has no where near the power of a Stihl MS261.
It is a better saw for trail work, its not like your going to be logging
with it, but it will cope with a 18" trunk across the path, will not do
it like a larger saw will, but the larger saw will be a lot heavier.
I do not like Mtronic or Autotune, its just something more to go wrong,
and you will need to take it to a dealer to read codes to diagnose.
The Echo, has an ordinary carb, easy to rebuild when or if required.
There is a cheaper Echo, 34 or 35 cc, also has a carb, weights 8lbs,
and is cheap to buy, talking about the 352 or its newer replacement
the 3510, with a 14 inch bar, or even a 12 " bar will do quite a bit.
If your going to be clearing trails, cutting close to the ground then
a longer bar will keep you from bending, 18" light weight on that
Echo CS-4310 would work well in that situation.