This is an interesting (and I suspect it will become far more interesting) as time moves forward. So far we have Audyssey (and its variants), Trinnov (and its variants), Dirac Live, and QSC (I suppose the 322, 922 variants) in play.
The QSC doesn't really belong in this list. It is a pro piece. It requires external intelligence to use properly (ie, no collective wisdom or opinion of others embedded in the firmware). It has no "automagic" function. Let's look at what is in that piece:
Gain Control (input, output, in line)
Mixers (including multi channel and matrix) Automatic and manual
Meters (you can see in real time what's up)
Signal Generators (any step in the chain)
Limiters (multi types and user defined)
--single shelf, multi shelf, etc., etc.
Compressors (multiple types and user defined)
Automatic Gain Control
16 filter types (all filters can be with another filter)
Graphic EQ (predefined width or custom)
Crossovers (multiple types)
Up to 8 different "configurations against a single inventory of equipment.
...and the list goes on.
What is missing? The "I'll do it for you" button. In other words, if you're scratching your head about what any of those things may do in the QSC partial list, then you should take QSC off your list of potential toys. It's only fair to mention that some of these capabilities would not be required in your specific configuration.
The QSC will not fix a bad room, compensate for bad speaker positioning, make up for a blown tweeter or fix a nasty timbre mismatch. Oh, neither will Audyessy, Trinnov or Dirac. They will all make the room sound "different". In most cases, we hope "better".
So what about these other guys? Who is to know at this point? Until Audyessy, Trinnov, or Dirac all send their gear to a single team of experts to fully analyze and compare side by side in the same room with the same equipment all we'll have is a bunch of arm waving about "my time domain is better than your phase domain" yelling and screaming. (Phase and time are synonymous kids.) Or, my microphone is smart enough to do vector analysis and figure out where the speakers really are against my microphones will do spatial averaging over a large seating area. OK. Enough already.
Audyessy, Trinnov and Dirac all have brought something to the table that has been sorely needed for a long time. They have sent the message to consumers that audio calibration is important. It is needed in any room and every room. Love 'em for that. However, any automagic function will be very, very challenged to win against a pro pushing the buttons and twisting the dials. On the other hand, the automagic functions are a far cry above "setting levels and distances".
So, let's look at a few of these.
If you're budget constrained, any pre-pro with a built in Audyessy or Trinnov is the way to go. Which one will be better? Under any specific set of circumstances the future verbal wars will be tantamount to discussions over triple flash, autostereoscopic, active vs passive, 50,000:1 vs 60,000:1 on/off contrast, etc. Both Audyessy and Trinnov will allow an end user (with the keys to the domain and the "kit") to tweak the automagic results within the limits of the software. Thats a good thing. Audyessy/Trinnov (built-in) plus a pro is cheaper than QSC + a pro. (I'm leaving Dirac out of this for a moment ... I'll slap them around a bit later.)
A standalone Audyessy or Trinnov (plus a pro) is likely cost neutral when contrasted with QSC plus a pro; but, understand QSC doesn't have an automagic button so you cannot have "different sound" while you're waiting for the pro to show up. On the surface, both Audyessy and Trinnov will do a good job and it would appear Trinnov is going to leave the pro with more options, control, and capabilities than you'd find in the Audyessy. It's not clear to me, however, how well Trinnov will handle spatial averaging. Right now, today, I'd take a Trinnov before I'd take an Audyessy; but, remember, neither of these outfits has any interest in sending out their gear to let me and my team beat them up for a few days. Sorry, Curt, an online demo doesn't cut it.
I'm not really buying into Richard's statement about gaining the same historical relevance as DTS, lossless multi-channel, Dolby Pro-Logic, THX-ReEQ, etc...but, I will buy him lunch if that happens.
Let's take a moment to look at what Dirac Live looks like. Well, lets not. It is not on my list of potential candidates. Why? From their literature (not hands on), it appears they have focused all their energy on the upper octaves leaving three less than fully capable filters for use below 200Hz. In small rooms, it the below 300Hz region that has the greater number of problems and issues to resolve. Very, very rarely (in a good room anyway) does one every really need to touch the upper octaves. They've also made some very suspect statements about early reflections and less than early reflections which would need some hands on before I'm willing to take a bite of that apple.
Now, if your intent is to have a high performance audio environment and you've gone to the trouble and expense to engage qualified outside assistance in getting that part of it right, AND, you intend to have a pro come in and perform the audio calibration, then use exactly the equipment they (the pro) tell you to use and get over it. These individuals (an Adam, Jim (Jamin), Keith, me) know exactly what we can get out of ABC and XYZ. MNO may really, really be good; but, unless you're willing to pay a pro $200 to $300 hr to learn on your dime, it's not a good choice. Further, each of these individuals are leaving their name and reputations in your room and taking on a new calibration processor isn't something they want to do on a customer site.
Trinnov and Audyessy do provide a capability not found in the QSC. That is the ability to synthetically create audio channels which do not exist in the original recording (aka ambience extraction processing). While the QSC will allow me to create (for example) a dedicated channel for height, it would not have the ability to derive what would appear to be height information, remove that information from a front/side channel and redirect it elsewhere. The value of doing that in a small room is questionable and for close mic'd recordings, of no value; but, to each, his own.