I own two. The Dyna-King Professional and the Renzetti Presentation. I like the Renzetti for the true rotary, the traveler will perform just as well, though. I have broken a plastic (it should be metal) screw that holds the rotary function on the Presentation. I emailed them to get a replacement and never heard anything back. That's a deal breaker for me. I won't own another Renzetti.
I like the Dyna-King because it's mulit-positional and I can comfortably tie flies from 10/0 to 26. It has 4 different postition adjustments but it doesn't have true rotary. This would be my pick of the two if I had to settle for just one.
You certainly don't have to start with a vise such as this but if you're the type that wants something that makes things easier, it's worth a look. I started out with a Dyna-King Squire. They have some good vises. As do other companies.