I own precisely four parallel clamps so don't have any experience to compare them to. They are Irwins that I got last year from HD on clearance for $20 each. I hate them. They are heavy and clunky to use. The jaws get stuck when adjusting/tightening even when the bars are clean. That said, they have tremendous clamping pressure so I still use them from time to time. I wouldn't buy Irwins again though.
Ernest Hemingway once wrote, "The world is a fine place and worth fighting for." I agree with the second part.