Going to the 5” Wilton machinists vise got you an 8” opening, over the 6 1/2 of the 4”. The 6” and larger models had cuts on the exterior of the jaws to bolt the replacement jaws to the vise, and, to my eye, created a weak spot right where it wasn’t needed. The 6 and 8 inch Wilton’s are horrifically expensive, the 8” is over 4K.
Comparing the upper end Wilton vises to products made 50-100 years past is like comparing an F16 to a Saber jet. The Wilton machinists vise is sealed, lubed, keyed, has an unbreakable nut, serviceable jaw facings, is rebuildable, and is built of superior ductile iron. It hasn’t had a century of abuse pounded onto it, and the company that built it is still right here, and will sell you the things you need to keep it going. I should get a set of smooth jaws for mine, but, haven’t, yet. The rubber faced aluminum soft jaws have been excellent, thus far.
There are two smaller vises in the shop as well, a 4 1/2” Craftsman that was a Christmas present from my Dad, and a tiny little Red Devil clamp on, that was his vise when I was a child. The flat jaws in the clamp on make it handy to straighten a cotter or nail without tearing it up, but, the small vises don’t actually get much use.
Some thought went into the mount that was built for the Wilton. Being able to walk to the back of the vise and having a clear shot at the anvil, as opposed to working only from the front, is a game changer. I’d never go back to having the main vise on the bench.