For clarity, nothing beats the 5.1 mixes of II and V, which aren't compressed as much as the new stereo mixes on the same DVD-As. However, the 5.1 mixes of II and V are conservative to say the least - 'big stereo' in the same way some of the Tom Petty 5.1s are. There's actually nothing 100% discrete in the rears in the 5.1 mixes of II and V, anything that's in the rear speakers is also in the front speakers at a lower volume, so what you end up with is sort of mono side-wall imaging for those elements.
I love the Chicago quad mixes, I think they really preserve the character of the original stereo mixes, while also having some of the weird quirks that I've come to love in mixes done for SQ quad. The quad mixes of these albums are my go-to versions if I want to listen to some Chicago now. Having said that (and I don't want to look a gift horse in the mouth, this set is a fairly priced godsend) I don't love the mastering on these discs. Craig Anderson may be a skilled BluRay and DVD author, but I think his relative lack of experience with mastering shows - there seems to be a one-size-fits-all approach applied to the whole set. There seems to be (relative to the LPs and CDs, which I'm intimately familiar with) a bass boost, coupled with some compression on the bass frequencies that make these albums 'thump' (especially the bass drum) in a way that no previous versions have, and I don't love it. The very high end has also been boosted somewhat, so that the hi-hats especially have a 'sizzle' that's kind of strident, but the treble boost is so high it doesn't add any presence to the instruments and vocals (ie stuff in the 5kHz to 7kHz range) which is generally what a good audiophile remastering focuses on.
On the plus side, these niggles aren't so major that they prevent me from enjoying the set, and the upside of them being PCM is that we as end-users can do our own remastering if we choose to - obviously it's laborious and time-consuming to do so, but it's a small silver lining anyway. I think if this had been mastered in a way that was more pleasing to me it would be an easy 10, but as-is I'd probably give it 8.5 to 9. If Warner/Rhino are going to do any more of these sets, I hope they'll use someone like Bruce Botnick to do the mastering - the sound quality of the Doors GH quad mix on the BluRay in the Doors Singles set is phenomenal, and bests the AF SACD by a wide margin.
As for bass being 'non-directional', I think it's overly dogmatic to cling to that. It may be true to an extent for LFE content in movies and TV (ie 40Hz explosions and rumbles) but for music I don't think that's the case at all. The fundamental frequency in a bass drum is somewhere around 60Hz (depending on tuning) and the fundamental frequencies of bass guitar live between there and well over 140Hz, frequencies that are easily directionally discernable. If you can't detect bass instrument placements as being in corners of the room, or in front or behind you, you may want to check your system, or your ears, or both.