The differences in dampening between an ATI and a Fluid damper are pretty small. Bracket racers would never notice the difference. NASCAR engine builders need to pay attention to this stuff though. I'm pretty sure all NASCAR engines get tuned ATI dampers these days.

For bracket racing or street duty just use whatever fits. For serious drag racing I'd probably use an ATI unit.

Finding something that fits is the important thing. ATI makes a version with a longer hub that fits belt drives and gear drives so that is one option I'd look at.