Bought a Stihl 4Mix trimmer about 8 years ago. Would have to walk to the garage for model #..... it was the lowest cost model at the time that would fit a Stihl brush blade. Light use around home, occasional use on a remote property for heavy grass/weed clearing.
I've been happy with it. Doing it again, I'd spend a bit more for one or 2 models up in Stihl, that at the time had a bit better vibration isolation. For light use (less than 30 minutes), it's not really noticeable, and when I do longer runs I try and make sure I have decent cushioning in the gloves I wear. Engine has good torque.
Not sure where you are OP.... used to be around here Stihl would extend the factory warranty no charge if you bought a 6 pack of Stihl mix oil with the trimmer. Good oil, and a bonus extension to warranty.
Only negative I've heard with Stihl is with bigger recent motors - a bricklayer I know had problems with a concrete saw - I think it was the muffler mount design changed, and didn't stand up as well to vibration - can't see this being an issue on trimmers.
Like poster #2, I've no experience with Echo.
Rgds, D.