Honestly, the Iregas are way better than WF. I have adjustable wrenches by pretty much everyone but Snap On, and the Iregas are the best. This includes Bahco, etc.
Irega adjustables are better in some ways, but not in every way. I own quite a few Irega and Western Forge adjustables, from 4" up to 18" in size. Irega movable jaws have a lot less up-down and side-to-side play when compared to my Western Forge adjustables. That is not always good though. If you are doing a job that gets your tools dirty or muddy, a Western Forge adjustable will be less likely to jam up with dirt, but in a clean environment the Irega mechanism will feel higher quality and more refined. The Iregas also often have metric and SAE measurements printed on the slides, and the handles tend to be a little more comfortable as well, because they are wider and flatter across the top so there's more area to push against with your hand.
Iregas have gone down noticeably in quality though, mainly since covid and the demise of Western Forge. Older Iregas had nice shiny smooth chrome on the sides of the jaws and better overall finishing. The newer ones have visible machining marks and what looks like vapor blasted chrome instead of shiny smooth chrome on the flat surfaces. More out of alignment adjustables seem to be making it off the line too. Top and bottom jaws that don't align perfectly side-to-side when the jaws are closed, jaws that have been mistakenly ground at a slight angle compared to the line of the handle, slide channels that are very thin on one side and very thick on the other, handles that have a slight curve to them from the factory, etc. Stuff that might not affect function, but that sort of visible garbage drives me crazy. The last Irega adjustable I bought was one of the 8" thin jawed ones, where the entire jaw is 3/16" thick. I had to buy three of them online just so I could end up with one that I found to be acceptable. That isn't just an Irega problem, but it's quite rare that I have an issue with a Knipex product or even a Taiwan made product, so they could do better if they wanted to.
For the same size adjustable, Iregas will usually open wider for most models, but they also often have narrower jaws than their Western Forge equivalents. That's partly why I own a mix of both. Iregas for tighter areas, work in clean environments, and for narrower fitting access. Western Forge adjustables for brute force tasks, work in dirty environments, and for grabbing fittings made out of softer materials like brass or aluminum, because their wider jaws help spread out the force better and reduce localized deformation of a fitting.
I would choose my Western Forge adjustables if I had to pick, because I find them perfectly acceptable and they are physically stronger. Online testing videos show them to consistently be around 30-50% stronger than Iregas before they distort or fail. That matters to me, but for someone like a homeowner who just wants an adjustable for occasional use it likely won't matter much.
Lastly, it's not true of all of them that were made, but my relatively modern WF adjustables have jaws that were ground a couple degrees out from each other, so the tips touch before the base of the jaws touch when the jaws are completely closed. That means even if the jaws do flex a little bit while cranking on them, they will end up parallel and still have a strong hold on a fastener instead of opening up wider than parallel and losing grip on the fitting more easily, like Iregas and most other adjustable wrenches that start out with jaws that are perfectly parallel. It appears that Knipex is now doing the same thing with their newer style pliers wrenches. Their original pliers wrenches had perfectly parallel jaws from the factory (I own several), and the lighter "2.0 version" pliers wrenches I bought recently all came with jaws that touch at the tip first and leave a small but noticeable gap at the base of the jaws.
