fisherboy - I own both of the vises you are considering.
I actually own two Regal Medallions - one with the standard jaws, and one with the stainless jaws. The stainless jaw version is rated for hook sizes 2 through 32.
The Renzetti can handle a bit larger hooks (sz 4 ?) down to size 32 as well.
Having tied many thousands of flies on a Regal and a Renzetti, I've found there's nothing the Regal can do that the Renzetti can't, but there IS things that the Renzetti can do that the Regal can't (ie true rotary techniques).
Then there's the "myth" of the Regal's simplicity of hook placement. Both the Regal and Renzetti require 3 steps to hold a hook.
Regal - squeeze lever, insert hook, release lever.
Renzetti - insert hook, rotate jaw knob, rotate cam lever.
The Renzetti actually only requires 2 steps if using the same size hooks, so you gain no speed at all with a Regal.
A stainless jaw Regal with pedestal base also costs almost twice as much as a Renzetti Traveler.