I have purchased pallets of broken OPE and echo is by far the easiest to work on, and seems to run the best even when wore out. The newer equipment does have more plastic on it, but it is still holding up quite well.
I also noticed that you can get used parts on ebay all day long for echo. Stihl / husky is not anywhere near as plentiful. This is huge for me as often in 10 yrs parts are NLA at the dealer, and you must resort to used parts.
Both trimmers will work awsome its just a matter of prefereance. Plan on using ethanol free fuel and a quality oil. If you cannot swallow that due to cost, just buy a fuel line kit and carb kit at the same time you purchase the trimmer so you will have it on hand when it fails. When using pump gas that is E10 or E15 the carb will fail. Its just a matter of when.
I have used echo with the "T" in the model and althought they sound awsome and do have lots of torque, I prefer the standard version without the "T". Echo has a science of using small engines that deliver excellent amounts of power for their displacement.
In ending, I have noticed a level of cost cutting in the husqvarna products that is not optimal. A great example is the 4 crankcase bolts on the 125L / 128L trimmers (and many others that use the 28cc engine). In about a year of commercial use and 3-5 home use the bolts will snap off and the engine will fall apart. Other models have other build flaws like cheap fasteners and hardware that is not suitable for commerical use. Gone are the days of the sweden quality 225RJ/235RJ trimmers that would outlast their owners.