I have the Milwaukee ones, and had seen and handled the Irwin ones in Lowe’s. The Milwaukee seem better built, and I too thought their handles were much more comfortable. Looking again now, looks like the jaws have a little more bracing in them than the Irwin, the pins that let the clamp surface rotate are metal rivets instead of what looks like all plastic, and I do remember liking the release and smooth feel of Milwaukee’s hex bar clamp/release mechanism better. I think I looked at the Irwin for probably 30 seconds and just said meh and haven’t looked at them again since. I use the clamps instead of speed bar clamps or C clamps for holding down levels to use as circular saw guides, or meter sticks to draw lines, hold wood in place on tables, all kinds of stuff. The hand clamps are just so quick to put on and off comparatively, it’s awesome. I haven’t had any issues with them sliding in my usage, the ridges in the head seem to keep a good hold (though they make light tracks in the wood too if you clamp them hard enough).
Milwaukee also has 4” hand clamps, which I have many more of them than the 2” and find them more useful, if you need bigger. I think HD is discontinuing stocking them, my local store hasn’t had the 4 inchers in stock for a while (pretty sure since I bought the only two from three stores I visited about a month ago). I’ve noticed stock numbers dwindling on the 2”, I’m keeping tabs so I know when to go buy them out, but the HD website doesn’t list them for online order anymore, and has them marked not sold in stores, which leads to that guess. I haven’t heard of Milwaukee discontinuing them though, and other places like Acme still have them, so you can still get them if you want, just possibly not in store. That is likely also responsible for the good pricing you’re seeing on them.
There’s also the all metal hand clamps Milwaukee has which are similar, I like the light weight of the plastic ones and find them more than sufficient and convenient, but if you need a little more oomph, my HD at least does still stock the all metal torque lock versions.
Going elsewhere or online, there’s even more options, Bessey makes similar hand clamps that are well reviewed, though I have no personal experience, and there look to be other brands as well. There’s also the little spring clamps which you can get in up to 2 inches, those things are super cheap and handy, though I don’t know if they’d work for your application, or if the large numbers of them you could get for the same $8 would help in any way.