That's interesting; I haven't seen saws like that before. I mostly deal with smaller limbs and have been quite happy with how quickly my 15" fiskars pruning saw and pole saw can cut through them. Those have a curved blade which helps to keep the relatively light blade in the cut.
I have a bow saw that I've used for some larger work but found it difficult to keep the cut straight. Maybe something like this would be a better option for me. Thanks for sharing!