Street gear drives, for the most part, are purchased for the sound they make, most of the time. A quality, double roller chain set -up requires less horsepower to operate and is race proven to very high RPM. Most racing timing gear systems consist of three gears (like a Danny Bee or Summers Brothers system).
A Pete Jackson type, dual idler would be advantageous if you had an unusual amount of align boring done, etc and a normal timing chain would be too sloppy (although you can buy shorter timing sets).
I guess there is nothing wrong with a Pete Jackson dual idler system, and if that's what you've got, it's gonna sound nice. There are two advantages to a gear drive I can think of and that would be less variance in ignition timing, and
you don't have to worry about your gears stretching like a chain will. I believe that a good true roller chain wins the performace per dollar hands down, but I can't really see where the Pete Jackson would be at tremendous disadvantage.