Unless something has changed, I believe that the Troybilt is still made by Ryobi for MTD. They used to be when the first 4 stroke TB's came out. I have a Ryobi 4 stroke trimmer that is identical to the early TB's, and it went 10 hard years of trimming without anything other than oil changes, and cleaning the air filter being done to it. I also used it with the tiller attachment to roto-til my fairly large garden after the plants got to tall to do any other way.
Still, I think you'd be happier with the lighter Echo.