I got the Ryobi one because I already had a couple of batteries and charger. I think it was around the £100 mark without batteries. This is the model that must be 4 years old now, still going strong. It has 3 sections – the base and hand where you put the battery, the cutting head which is adjustable angle for doing hedge tops, and the central sections, which you can leave off for doing stuff that’s not quite so high.
It will get through stuff 10-15mm thick easily enough – the difficulty is holding it still enough to chew through in the same place.
It’ll get loads done with a very modest amount of battery.
I’ll echo what Carlos says about the long pole ones being unwieldy and heavy. Unless you’re stacked, you’ll get tired pretty swinging it around (max length must be 3 m+) but that’s still far safer than ladders IMHO.
It’s still quite heavy and long for doing close work on hedges low to the ground, so you might find you still want a small one, but maybe get corded for that.