cso has the best compression and is prob the most used these days. although cso compression can cause lag in some titles, in which case i use the standard iso format. hope that helps
to me seems like pot luck to what i get working i have tiger woods running very nicely in cso , but i have most of my success with iso , so if you have the space on the mem card , stick with iso`s
kind regards biffo
Its all about what your priorities are really, whether its speed or size
ISO - Good speed but abit bigger than the rest
CSO - Alot more compression (good if you've only got a small MS) but of course its alot slower