I bought a Ryobi 14" 40v and I love it! The first thing I did when I bought it was cut down a 40-foot tall tree. Then I cut the whole tree up and still had battery left over. That was enough for me.
RYOBI 14 in. 40-Volt Brushless Lithium-Ion Cordless Chainsaw, 4 Ah Battery and Charger Included-RY40530 - The Home Depot
That's all I carry in my Pioneer on the trails. My father has a Stihl MS290 that I can use if I need a bigger saw, but I haven't needed it yet. I carry it in this case:
Power King Universal Chainsaw Case-CSCAU - The Home Depot . Which has storage for oil, extra chains, wrench, extra batteries, etc. I bring with 3 fully charges batteries and my small inverter and a charger, though I haven't needed them yet.
I wanted to get one of those external mounts from Kolpin or Northern Tool, but so far I've happily kept it in the case especially if my 3 and 5-year-olds are with me in the machine.
I also bought the 40v trimmer from Ryobi and it has more power than the gas one that I had prior, and it came with another charger and battery. I can do the whole yard in about a half battery. I trim around 20 trees, 3 small sheds, a swing set, and my house (2 acres). I have been very impressed with these cordless Ryobi tools.