I love my Regal! The majority of flies I tie with it are in the size 8 to 3/0 range, but I have tied down to size 22 with it. I mainly like the simplicity of it's design, and have owned several other vises in the past. Have not had a Renzetti however so can't comment on them.
The only con I can express about the Regal I have, as it has the standard jaws, is for me it won't hold all the larger hooks I might use. It doesn't hold all 2/0 or 3/0 size hooks, depending on the wire diameter, as a heavier wire may not fit into the jaws. Those are 2 hooks sizes I use a lot.
Since most of the tying I do is for warmwater or saltwater species, I would go with the big game version if I was purchasing another Regal.
I've had this vise for so long now, I got it before they offered the jaws for bigger hooks! Can't recall exactly when I got it, 30 years or so ago I think.
I've literally tied many thousands of flies with it and it's still going strong. (Tied commercially for 15 years.)
I also tie jigs, and have tied them on up to 10/0 size hooks. No commercially produced vise that I know of will hold a hook that big, but for the size range on which I primarily tie flies, I love the Regal!