Speaker grills on or off?

My paradigm studio's (v.5) all sounded more cohesive with better imaging with the grills on. I think they were designed so that the grills helped with dispersion and less diffraction.

Can't really tell with my kef's. They may sound more crisp, slightly better details with the grills off but it could just be in my head too.

Both my kef and my paradigms looked equally good with grills on or off but because my paradigms sounded better with them on, I left them on. My kef's grills come off and then go back on every couple days just cause I'm weird like that.'

I agree that dome speakers were designed with them to stay on.

Here's a thought; why not one on, one off ;-)