If you do a quick search of the forums there is plenty of info about codecs and which are best.

It still depends on many factors - whats in the clip, is it a feature or just a background. Some things look great as DV, others look ordinary. Some things are fine as Photojpeg 50% others need to be at least 75% to get the best compromise between speed and quality.

At the end of the day it is what satisfies your eye or that of the person paying you to do it. Best to at least test a couple of the options.

I am pretty sure that Catalyst defaults to High Quality mode regardless of what the Quicktime Player preference is. It has always appeared to do that for me.

Cheers

Toby