THX processing and Yamaha Cinema DSP processing differ quite a bit.
THX processing adds decorrelation to the left and right surround channels when they contain identical sound, essentially shifting the sound out-of-phase between them to spread the sound and reduce speaker localization. It also adds timbre matching to the surround channels to compensate for differences between surround and front speakers, and re-equalization to the front channels to compensate for the high-frequency emphasis (X-curve) in movie soundtracks.
Those are all pre-configured to THX specs and THX processing is not always appropriate. It assumes the soundtrack isn't already adapted for home reproduction, and you can't really ever know for sure if it is or not. When a soundtrack is sweetened for the home video release, I guess THX processing can actually degrade the sound. I'm not entirely sure though.
Yamaha's Enhanced Surround mode uses their soundfield processing to put an array of "virtual surround speakers" and acoustics into the soundfield instead. It basically tries to emulate the acoustic environment in a typical movie theater (albeit more modestly than their Movie Theater modes). So, it's quite a different beast than THX processing and may feel more spacious and inviting.
So, THX processing and Cinema DSP are almost complete opposites, sharing only that they're trying to improve the listening experience in a home setup. While the philosophy of home THX is to make the environment have as little effect on the sound as possible, as in THX certified movie theaters, and THX processing only to emulate the speaker setup used there, the philosophy of Cinema DSP is simulating the sound when the environment does have an effect on the sound, as in traditional movie theaters.
Personally, I feel that with vanilla settings, the Enhanced mode is a bit too active. The good thing is you can play around with it though, which you can't with the THX processing.