I was given a pair of the Kleins a year or so ago, they're still in the original wrapper in a cabinet of spare tools that I have. They looked, like they were just an updated licensed copy of the Ideal model mentioned above, if that's true... they're simply amazing.
The Ideal model mentioned above has been the gold standard for industrial wiring for a long time. They're really appreciated when you're working in a panel, landing hundreds of wires. They also meet the specs for the termination manufacturers, which is critically important in certain industries. I keep about 3 of them in my wiring box (of different wiring sizes), and the more commonly used (10-12-14 model) in my general work tool bag.
How do those versions compare to the Irwin's? Are they supposed to be better or something?
Yes, they're better (specifically the Ideal model mentioned above). They've been out a long time before those automatic adjusting ones started being licensed by everyone for automotive electrical work. They're almost always aimed at automotive wiring and almost never sold by industrial supply houses, as I believe they don't meet the higher standards for wire stripping/terminations. If you look at the specs for the Ideal, they're within thousandths of a millimeter, for proper insulation stripping without damaging the conductor. In addition to them having different Blades for different types of insulation. The automatic kind, like the Irwins, will never have that level of precision. Which likely isn't needed for simple automotive wiring, but is required with many types of industrial wiring.