My father in law bought a DR trimmer in the mid-90s to use at his lake house. I used it helping him clear weeds and small brush and was impressed with everything but the price. A year or so later I bought a Cub Cadet brand that was much less expensive and was very disappointed. It was not even close in mowing ability and was a real PIA to keep the string on the hub. If I hit a post or any solid object the string would pull out and the cutting height wasn't adjustable. You get what you pay for applies....
When we moved to our new house, I bought the commercial model DR with electric start to use and have been very pleased with it. I mow tall grass, weeds, green briars, privet, and honeysuckle sprouts with ease and keep my fence rows clean and the shore around my pond trimmed. No problem with the string at all, mowing height is adjustable, and the adjustment stays set during mowing. It has been well worth the extra money. BTW, I gave the Cub Cadet trimmer away... live and learn the expensive way.
Bill