I don’t know very much about them, but the one we own we have to mix the gas with oil I think, can’t use straight gas. That is something to think about, do you want gas or electric? They may even have ones you charge and works on batteries? Not sure. We have a very big lawn, so my husband chose to not have to worry about long extension cords. Ours has a plastic wire that is whipped around to do the cutting, it works pretty well. We own a Craftsmen and we have never had a problen with it. We have owned it over six years, and our grass grows about 7 months a year.
If there are options that use a different system than having to use the plastic wire I would consider it, to not deal with having to put it in so often. I guess the good thing about it is you can get really close to trees and not risk damaging a blade. Even a blade you need to replace or sharpen eventually.