I own a variety of clamps, and only recently started using parallel clamps. I own a few from Irwin and Jet, and I tried the Bessey clamps in the store. I recently got a sale flier from HF with a ridiculously cheap price on their parallels, so I had to try them.

Overall impression: Better than the Irwin and Bessey clamps, not quite as good as the Jets but 1/4 the price.

All of these clamps (Irwin/Jet/HF) have nice big handles. The Jets are hard plastic with three rubber strips for good grip. The Irwins are all rubber, and the HF are solid aluminum with a grained finish. That sounds less comfortable, but it's not, and gives excellent grip. All of the handles are just fine for comfort and power.

The Irwin has the largest jaw face, and the HF the smallest. All of them have smooth jaws that stay parallel.

The mechanism on the Irwin is the least desirable. It has a locked and a loose setting, but nothing in between. In the loose setting the head will slide with little provocation, making it very hard to pre-set them and then use them one-handed while holding a work piece. The Jet clamps have a release trigger, so they are locked in place until you pull the trigger. This is pretty easy to use one-handed. The HF has locked and loose settings as well as an in-between setting where you can move it with direct pressure but the head doesn't just slide around on its own. This is very easy to use one-handed. The Jet and HF clamps have teeth on the bar to lock the position, while the Irwin does not, which is why this works the way it does.

The bar on the Jet is shiny and slippery, resists glue. The others are rough and glue does stick more easily. The Jets have inch markings on the bar, which is very useful. All of the bars are much stronger than needed for any amount of hand pressure you can apply, so bending is not an issue.

If I was stocking up today, I would buy a few Jets as my main clamps and HF for my backups. The Irwins are inferior to the HF clamps in most ways, so I wouldn't buy them again. The Jet four-clamp cabinet kit is a good start, with two clamps of two sizes and four of the square-up clamp holders included, as well as a set of bench dogs.