Personal preference, but I've found that even if I sit down and carefully and thoughtfully compare two modes I probably hear a difference but am unable to judge one better than the other.
So I default to being a victim of marketing and select THX because I like Tomlinson Holman.
Most of my listening is done to classical music. And, for that, I go to live concerts every couple of weeks on average. I have decided that for me, the closest approach to the sound of a live concert is plain, DSD input for SACD's, straight PCM for DVD-A's, or straight DTS MHD, Dolby THD or LPCM for Blu-ray music, all with Audyssey on. It helps that I have some recordings of live performances I attended. Of course, they were recorded several years ago.
I don't listen to stereo any more, but if I did, I would do it in plain stereo. Some of my friends like the multichannel effects of certain derived sound modes. But, I think I would rather stay closer to what the mastering engineers actually heard.
For movies, there is no independent reference standard. I don't know exactly what Meryl Streep's voice sounds like in real life, since I have never spoken with her. I do not know if the sound of a car crash, an explosion, or some other sound effect is accurate, because they all sound somewhat different in real life, and we do not know exactly what is on the movie sound track. But, I am quite content with the straight, unaltered sound track as recorded.
I do use Dolby PL2X for TV, with decent results, for example with sporting events. But, I do not listen to TV sound very critically.
I have not really liked imposing THX on any sources. My speakers and system are very fine but not THX-compliant. I think proper use of THX requires the use of front-rear facing dipole surrounds to give a more diffuse, "fuzzy-wuzzy" effect. And, though I too deeply respect Tom Holman, I am not really happy with THX on my system with any sources. Using music sources, it certainly delivers what is to me much less in the way of faithfulness to live concert sound.
If it's not obvious, my theory is that if it sounds "right" with music vs. my recollections of live concerts, it ought to be right for movies, too. No doubt some synthetic sound modes, like THX and others, can produce different effects, and some may prefer them. But, I think avoiding them brings me closer to what the mastering engineers heard, and that is what I prefer.
Audyssey EQ on is mandatory for all my listening. I have become very sensitive to bass boominess, hangover and other room/speaker artifacts since I have started using it. So, eliminating those is not just important to me, it is critical. It makes a huge difference for the better, so there is no going back for me. (I recently attended a demo of Wilson Maxx's with D'Agostino amplifiers. It was spectacularly UN-impressive due to the poor acoustics of the demo space. My own system sounds way, way better than that at a fraction of the cost. Audyssey has a lot to do with that.)
I have not found any other Audyssey features - Dynamic EQ, etc. - necessary or useful. To me, they take away from musical realism. I have not been interested in trying DSX for the same reason. I have yet to see a review that values it highly for music, though I am sure that many will like the effects it produces with movies.