Power Scythe vs hedge trimmer -- what's the difference?

[Wild Turkey73]

I need to reach under hot fences and cut blackberries, wild roses, etc. so they don't short out fence.

The scythe and the adjustable trimmer both look like they would do the job but I'm wondering what's different -- is the scythe designed to cut heavier stuff?

Tool descriptions don't help much, even my dealer looked it up with no luck.