I have 40+ acres timber ranch and for fire prevention, we like to keep all lower branched cut off to about the 10 foot mark. So I bought a Honda UMC-435 power head, bought the pole saw extension for it and the added 4 foot extended center section too. Its a bit heavy, but it comes with a load bearing harness so your arms are not holding it up, just controlling it, so the power head is on my right hip. It rips right through the big branches with ease.
I also have a Fiskars manual operated pole saw that cuts on the pull stroke and does a nice job, but if you have lots to do, the power unit is the way to go.
This Honda power head can be used with the edger, line trimmer, tiller, brush cutter, loads of attachments for it.