Have both in the Regal - tru and rotating. Never use the thru and hardly ever rotate..
I taught myself to tye on an import - using the head and barrel for a "hand rest". With the tru in line vise the jaws are separate and away from the vise body (except for Nor-vise & Regal tru-rotary). I still hold the hook (while it's in the jaws, when adding materials that I have to crank down on. The jaws can hold the hook fine - I don't want the shaft, of the hook, to be bending back and forth. The friction and heat will change the temper of the hook.
For me - tying flies is a Lot more "gentler". I don't pull or crank down like when I'm tying jigs. On the other hand - I've watched one of the most prolific tyers that I know (JJ) whip out the jigs on a Renzetti Traveler.