Finn is correct on the brushed vs fuel. I have the fuel(great) and I used the brushed version the other night at work to cut a 2" pipe. What a piece of ****
The hackzall has half the stroke of a sawzall if I remember correctly.
I use my M12 Fuel hackzall for pruning trees with a 10 inch carbide pruning saw blade. It is very handy and light enough with a 3.0 battery to hold with one hand on a ladder. But the short stroke makes it less than ideal for anything bigger than say 1.5 inches. I dropped a 6 inch oak tree with it but that job took more than a few minutes. Ideally, a guy should have an M18 chain saw in his arsenal. Different tools for different jobs. You don’t need a chain saw with a 12 inch bar to prune a Camelia bush or a 50 year old 6 foot tall and 10 feet wide Japanese maple.