Jaws are arguably the most important part about a vise. Frankly, though, too much emphasis is placed on the hook-crushing power of jaws (few actually can, by the way). You want to hold a hook in the jaws
not a truck. You need to be able to set a hook quickly and easily into the jaw, and clamp it just tightly enough, without excessive effort, so that it won't move while you're tying. We can pretzel 3/0 stainless hooks, too, but clamping a hook that hard means your vise is working too hard, and it also means you're working too hard.
HMH jaws are hardened tool steel, and they are guaranteed to last a lifetime. The shape and profile are carefully designed so that you can put enough steel on a hook to hold it well, BUT also so that you can actually get to the hook with your fingers so you can position materials. Access to the hook is the most important thing in fly tying, and no other premium vise manufacturer out there can give you the unencumbered access to hooks that you get with all HMH vises and jaws.
All-around jaws are a fine idea, and our Omni jaw is brilliant at a wide range of hooks. But if you're serious about working on extreme hook sizes, say, #20s and smaller, or above 2/0, then you should consider the vise that gives you the jaw that's best for the job.
Not real sure what else we can say about the hook holding ability and longevity of HMH jaws except maybe to tell a little story. Pacific Fly Group, a commercial tying operation out of California decided they were tired of buying vises every 6 weeks or so, so they invested in a bunch of HMH's. About 8 years later, they sent back one of the jaws, saying it was a bit worn. We gave the jaw a new edge and sent it back. We asked them to check their records, and they then informed us they figure that jaw had ted more than 150,000 flies. We'll be glad to fix or replace your jaw, too, even if you haven't tied that many flies.