The only other discussion I found on an A & H was regarding the monitor console so I'll reply here.
I use the A & H GL2400 every night at the club I work at and find it to be a very capable board for its price range.
A few things I like about it:
-Aux sends come pre-insert and pre-eq. So if you're mixing monitors from FOH the musicians don't hear the eq changes in the wedges while you're mixing. And, if necessary, you and adjust the output of an inserted comp and not have the level change in the monitor.
-The master section has a separate fader for the mono out. I use it to send signal to the powered sidefills we have. I just cover the input panel on the speakers so the dj's don't mess with it and control the level with the mono fader next the the L/R masters. I don't know if thats useful to you but maybe if some video guy comes up last minute and asks for a feed to his camera the easiest thing you could do would be to send him that and have control of the level you send him.
-Each channel has a pre-eq direct out, and a line-in, I noticed the mackie just has the line-in and no direct out on each channel. Its also very useful for a recording or sending a signal to a separate mixer if you don't have a proper split for each channel.
-I find the matrix section on the A & H very capable, if you ever need separate submixes for a recording or anything else you'll probably find that will handle it no problem. It has an external in and and output for each one of the 4 matrix groups. The mackie just has an A/B out for the matrix section.
- Although they both have a pad, phantom power, and the hi pass filter on each channel, the A & H has the polarity reversal button on each channel. I personally don't use it very often, but its nice to have, the mackie doesn't have it.
Although I've never used the Mackie Oynx 32.4 Mixer, I will say my experience with mackie boards has been nothing but bad. Granted, I've only had to regularly use two of them in my experience, but 0 for 2 is not a good start. When I was in audio school we had a digital mackie that gave us nothing but problems. For the year I was there it must have been sent in to mackie for repair about 6 times, and not once was it ever usable for more than a week. Also, when I first started at the club I work at now we had a 32 ch. mackie desk. For whatever reason, although it was covered every night it seemed to be highly susceptible to dust and whatever else. One by one, the channels just kept crapping out without warning until we finally upgraded to the A & H and its worked great with no problems for the last year and 1/2.
I've had a couple uppity soundguys come in a scoff at our A & H, but thats because they're probably used to mixing on soundcrafts and the like, certainly not because they prefer mackie.
So Phil, as you might have guessed I'd say hands down go the GL2400. Besides the previously mentioned features that the mackie doesn't have, the fact that the mackie has a built in comp, is very negligible with everything else considered. Regardless of how well it works, go with the dbx quad comp you mentioned and you'll be better off either way. I use 2 of the dbx 266xl dual comps and they work great(for live sound anyway). 2 of those are actually still cheaper than the dbx quad comp, about 200 bucks cheaper actually. So theres another option for you to still get 4 comps and save some money. It'll take up another rackspace but, I'll gladly save 200 bucks and use another rackspace. I think one might be hardpressed to find a noticeable difference between the performance of the two comps, I've used them both and they both work great for live applications.
Good luck.