most of not all 1st party PS3 titles that support DTS will automatically choose DTS over DD by default, I remember Bad Company 1 was also default to DTS.
I think even third parties too with a few exceptions, even with LPCM. Capcom's MT Framework games have LPCM and DD options but DD is the default.
I think Tekken 6 goes to DD instead of DTS if you uncheck LPCM. The DTS option was incidentally a 3 speaker mix mostly.
As far as fidelity and quality of editing, Uncharted 2 and Batman AA impressed me the most. The latter was a pleasant surprise all around.