Room correction, which is best and what differences are there?

Ill do a quick summary of what I've found but remember that things will be different depending on your room and speakers. There is no way to know which will work well or not in your room so you will just have to try them and see. I have not used Anthem's ARC or Hk's EzSet EQ so I won't put them on the list.

YPAO - Also never used. The lower models don't EQ a sub so I wouldn't buy anything below the 2010 or 3010 which I have never really found in my price range.

MCACC - Doesn't EQ a sub on any model. I like that you could run it different ways and get a different sound. You can save up to 6 different versions and its easy to flip though them to see which sounds the best. The problem was that I never got the sound up to the level of what I have with Audyssey. Bass didn't seem as deep or powerful and I didn't think the soundfield was as cohesive. It wasn't a blind a/b test so I could be wrong but thats just what I thought.

Audyssey 2EQ - Never used. No sub EQ so I would not buy a receiver with 2EQ.

Audyssey MultEQ - Did an excellent job with my system. I am in a small room and it was able to tame the brightness I sometimes heard before having it. It created a more realistic surround expereince as well.

Audyssey MultEQ XT - The highest version I have used and it also works very well. I have found few differences between it and regular MultEQ. The only improvement I really found was a slight increase in dialog clarity.

Audyssey XT32 - Never used. Has the ability to EQ dual subs. I am currently trying to figure out which receiver to get with XT32.

I have tried MCACC, Audyssey (XT and XT32), and Anthem's ARC.

Personally, I prefer ARC over the other systems I have tried.

ARC in Anthem receivers will only work up to 5000 hz. You need to move to their high-end separates to get full-range correction.

There is ARC by Anthem... I have this on my AVM-50v and it EQs the full range.. Excllent and many say as good or bettyer than XT32... I have not heard XT32 thogh... only XT and a different system so no real compare can be stated.

Room Perfect in McIntosh high end

Trinnov in ADA Mach IV or stand alone system

There are a few others and then there are the standard PEQ used in CLasse SSP-800 , ADA Mach IV, older B&K etc.

I had a B&K Ref -30 the PEQs were good, very basic and took a lot more gear to set up and dial in.

Modern EQs are self contained and very easy to set up, which is one of the best reasons to have them over a PEQ.