I went through a bunch of consumer grade string trimmers (2cycle, 4cycle and electric) before I came to the realization that spending more on a pro-sumer/commercial grade trimmer would be less costly in the long run. I had already upgraded my mower, generator and power washer and was pretty thrilled with the 4 cycle Honda powerplants, so I began my research already favoring the 4 stroke Honda. I also had good experience with Stihl, Echo and Husqvarna equipment so those were at the top of my list with Honda at the get-go. My poor to fair at best experience with MTD brands (MTD, Ryobi, Cub Cadet, Troy-Bilt, Craftsman), John Deere (small consumer mower) and Weedeater eliminated them at the start. My experiment with an electric trimmer (Black & Decker 18V) was a miserable failure, so it was an all gas powered quest.
After researching landscaping forums online and talking to a local small engine repair guru as well as local outdoor power equipment dealers I narrowed it down to 3 trimmers, the Echo SRM-S30, Shindaiwa T242 and the Honda HHT25. I think I would have been happy with any of those but ended up with the Echo SRM-230. Shindaiwa had the weakest local dealer, so I eliminated it first. The best local servicing dealer of Echo and Honda was one that I was already using for Stihl, Echo, Honda and John Deere equipment, so it came down to hands on feel and price. I liked the feel of the lighter Echo over the Honda, it was cheaper and the dealer seemed to favor it as well. It's been about 2 years now with the Echo and it still runs like a champ.
I only use an ethanol-free pre-mixed stabilized fuel in my 2 cycle engines. It's expensive, but I figured that the professional landscaping maintenance contractor that recommended it to me felt it was worth paying extra for, it just might be well worth it to me. I have been using it for a couple of years now and the only thing I have had to do on any of my 2 cycle engines is clean and/or change the air filters.