I have a dual boot, dual 1 ghz G4 (Logic/TDM in OS 9 and X on separate drives) and was advised by the very wise Nick Batzdorf that Gold does not work so hot in OS9, so go with OSX. So I just installed in OSX and he's right, it works quite well. In fact I was quite surprised at how well and how much I could load.
Lee's also right. OS9 has been abandoned in terms of support by most everybody, so its good to get up to speed in OSX any way. Believe me, I held on tight to 9 until recently, because of its stability. But it was finally time to get on board with the new stuff.