Wish I knew a buddy or a local dealer, where I could have tried the Stihl. I was really skeptical of the 4-mix engine (4 stroke using 2-stroke mix), and how it compared to an ordinary 2-stroke, like the Echo uses. Something tells me two power strokes in the same amount of time as a 4-stroke should be more powerful in an engine this size, but I realize there's so many variables it'd be hard to compare the two on paper. I wanted something powerful, and can't buy both, so I went with the familiar 2-stroke. I'm not disappointed.
I went and bought a 4-stroke Troy-bilt power head for my cultivator, and I'll be darned if that thing doesn't perform as well as the Echo, with the string trimmer attached. The Echo does a better, faster job if you're using it like you should-- broad strokes across the weeds/grass. It'll get down and dirty if you just plunge it in, but it does bog down in really thick stuff. The Troy-Bilt 32cc 4-stroke, it has three sounds: a) normal, b) under load and c) you buried it and it's not spinning. It doesn't require the finesse that the Echo does, it just tears through stuff. But it's also much cheaper built, you can tell the second you pull it out of the box, when you see how bad the plastic is molded in some areas. I'll use it solely for my cultivator which hardly gets used, and it'll function as a back-up string trimmer.
I can certainly agree with 2=1, 1=0. I have a lot of lawn to take care of, and things will break down when you least expect it. I hate scrambling last minute, nice to have a backup.