joe buy the best hedge trimmer you can afford. I made the mistake of buying one at Home Depot for about $100.00 and it does a half baked job. I think the key is how big a bite they can handle. Not the length but how big a branch they can cut. I think mine is rated at 1/8 inch and it can't cut the mustard. It looks pretty good in the original box out in the shed.

Take a look at the Little Wonder hedge trimmers. Don't let the name fool you. These are commercial quality machines. My hedge is 125' long, 6 to 10' wide, and about 15' high. My Little Wonder is a double sided 24" machine. It works great. I think they now sell for just under $200. Charles Ranheim

First off hedge trimming is shaping soft green growth.
You need to renovate this hedge which means dropping a few inches below the height you want to finish at with saws and loppers and then maintaining the finished height by trimming the new soft growth.

Otherwise you will just ruin any trimmer you buy.

If you want to buy a new one every year or two get a cheap one at the box store, otherwise invest in one that will last a lifetime , in electrics that means little wonder.

I know that if you buy a Little Wonder trimmer, it will last the rest of your life. Believe me. We have used them for 30 years professionally and they can't be beaten. Anything else is junk and probably won't last you for one year.

Looking at the gas hedge trimmers. Single edge or double edge?

The ones coming in for re-sharpening are mostly double edge. , there is little difference in the rest of the machine besides the blades.