The Omni looked like a really cool idea the first time I saw it. In what, the 1980s?

Then I found that, to follow the instructions and mount it right side up to hold a ten pound speaker, I could not tighten it enough with the supplied wrench. I could use a ratchet, but that would not fit under the mount with the speaker in place, so I got a 14" extension for 1/4" ratchet drive. That told me that they do not quite have reality on their side.

Crunching a plate with bumps down onto a plastic ball sounds like a great idea, but I have never seen it work without sagging. It just occurred to me: adjust the mount, get the arm JUST where you want it, then take the speaker off (don't ask me how). Heat the mount with a torch so that the metal bumps melt into the plastic ball, then tighten two more turns. THAT should hold it!

I would not use an Omni for a plasma. Ever.

Chief is about as overbuilt as you can get. I would expect a Chief to hold a locomotive out at three feet. I have seen one sag the tiniest bit, but it would take some convincing for me to want a different mount.