One of the features of the 1.9 firmware is the ability to force 24hz output for Bluray. I have a Panasonic TH-PZ700U plasma that has the ability to convert 24hz sources. Would it be better to let the PS3 or Plasma do the 24hz conversion?

What does your plasma convert 24hz sources to? If it just converts them to 60hz then it won't be any different than turning off the 24hz output option on the PS3 so it handles the conversion.

What does your plasma convert 24hz sources to? If it just converts them to 60hz then it won't be any different than turning off the 24hz output option on the PS3 so it handles the conversion.

My plasma is native 60hz so would it make any difference whether the PS3 or Plasma did the conversion?

Nah, coverting 24hz to 60hz is just a matter of runing a frame for three refreshes and the next one for two and so on, it doesn't matter if it's don't by the TV or the PS3. The 24hz option is really just for displays that will actually refresh 24hz or some multiple of it when getting a 24hz signal.