Mac OSX is great, but obviously, not all of us have carbon or cocoa apps. With apps such as Quicken 2000 and Photshop 6- should apps such as these be installed when booted into OSX or OS9? Is there a better choice, or maybe it doesn't matter? I install all OSX apps when booted in OSX, but what about Classic apps?
It's possible to install OS9 apps in Classic mode. However, not every app will like this, so peruse the readme files for guidance. If you can't find anything specific, boot directly into OS9 to install.
I strongly recommend installing classic apps while booted into 9. Also, if you use apps that need plenty CPU and ram, boot into 9 when wishing to work in them. They will perform much faster than while in classic mode in X.