I have 3, an Echo, a Stihl and battery powered Black and Decker. For quick trimming around the front yard I'll grab the B&D every time. No gas to mix, never, string never, never jambs, automatic line advance (never once had a problem), head rotates for trimming or edging along the driveway.
As for the Stihl, this **** thing jambed on the first use. Took out the string, rewound, used it for 5-10 minutes and it jambed again. Bump the head on th ed ground, nothing, string melted together. Bought the newest head where you cut a 12 ft lengrh of line, run it halfway through the head and just wind. Jammed in minutes. Switched to the twisted line, and that helped considerably. Still will nit advance half the time. Carburetor fine jets clob on Ethanol gas (same gas i use in Echo). Well bu il lt other that that.
Echo works better but also has head problems, just not as bad as Stihl. Carb does clog as well, but not as easy.
As i said, for fast work, small areas (based on battery life) battery powered B&D works best. Absolutely no problems other that maintaining a charge.
With any gas-powered trimmer, follow these rules for best operation.
1. Use NON-Ethanol gas. Ethanol gas will seperate out and the alcohol WILL burn the valves and possibly melt a hole in the top of the piston. Secondly, Ethanol draws moisture out of the air to itself. This forms gunk that WILL clog the tiny jets on a modern gas carburetor.
2. If you cannot find Ethanol free gas, before you pump gas into the gas can at the service station, add a preservative to prevent seperation. I use both Sea Foam and Sta-Bil.
3. Use a co-extruded type of line to prevent (or at least lesson) line tangles due to it melting itself together.