I bought a cordless one of these c. 18 moths ago from Lidl, I already had a set of batteries for this, which brought the cost down. This has a length of 1.9 to 2.7 m.
First up, I would say that you want to get one with the shortest reach that will cover your needs. If you only need a reach of, say, 3m and you get one that will extend to 4m then you are carrying - and more importantly holding up in the air - unnecessary weight.
It is not just the weight but how unwieldy it is. With something that is 2-3m long, moving the far end just a couple of inches is hard, as that involves a very small and precise hand movement.
I have a couple of (very old) manual pole pruners, a set of lopper like jaws on the end of a long pole. Those are limited in what they can cut so when I saw the one in Lidl I was basically 100% sure that it would be useful, which it has been. So I did not look into them in detail but my understanding is that there are various options. In increasing power:
- Cordless electric
- Corded electric
- Petrol
Also some (like mine) run electric cables up the body and have the motor at the top. That makes them more top-heavy, more unwieldy.
Others, AFAIUI, have the motor at the bottom and a drive shaft up the body. This makes them heavier overall but less top-heavy, less unwieldy.
Weight is also an issue. Mine has a shoulder strap that goes diagonally across the body and is very useful in taking the weight and keeping the whole thing balanced.
I only use mine for short periods at at time, e.g. 5 minutes cutting then at least 5 minutes breaking down and clearing the brash; repeat for up to an hour. So the shoulder strap is adequate. With a heavier machine, using it for longer, or both, a proper harness might be better.
Mine came with an Oregon bar & chain. As that is what actually does the work it is important to have something good.
Because of the difficulty of accurate positioning, I find making clean cuts hard, even when I take off most of the weight first and then do a second cut. This is not much of a problem for me as my garden became (under earlier ownership) rather a jungle and I am mostly cutting back weed trees (laurel, holly, etc), but if it is a tree that you care about this may be an issue.