I am not suggesting you can replace your chainsaw, but I like using my cordless recip saw when I climb trees.
Not as fast as a chainsaw, not even close, but quiet, light and not smelly.
Their safety can't be overlooked either.
If speed is your deciding factor, they're not for you, but if you're not in a hurry and want to enhance the in the tree climbing experience, you should give it a try.
My preferred blade;
https://www.leevalley.com/en-ca/shop/garden/garden-care/saws/71675-lee-valley-pruning-blade-for-reciprocating-saws?item=EC680