elamb,
Shindaiwa.
We have one at my families driving range. It has been in continuos use since 1988. It is still going strong with just annual tune-ups, and this thing has been abused. You can cut a tree down with it, came with 2 saw blades. I bought one for the house too, and one of their chainsaws. Never had any problems with any of them. They are a few dollars more then the brands you mentioned, which we have an entire wall of at the range, all are toast. I haven't looked at any in a few years, and I am assuming they have kept their high quality standards, but you will not find any better weed eater out there.
Just my . 02
Mike