Mark,
Doesn't the MacBook Pro Retina come with 8GB of ram these days, by default?
In which case, not running Logic in 64bit mode is strange as you are not getting anything like the performance out of your MBP and Logic (or Live for that matter), that you could, by doing so...
It's an odd attitude to take.. when you say you neither care for or wish to test 64bit mode.. given the clear benefits in doing so once you have at least 6+GB of ram on board... but then, each to their own.
As has been said several times in this thread and elsewhere.. Don't just submit a ticket.. Call them and get a Case ID.. and use that Case ID in every communication of any kind you have with Apple in regards to this issue. Doing so forces a different set of actions by Apple's support dept... and as I have found, often leads to much more communication from Apple in return.
As an example of the benefits of using Case IDs... I had a long standing issue with Logic and an external FW HD connected to my Mac via the TB to FW adaptor... that was driving me nuts. After two months of files and logs being sent back and forth between myself, two other people who reported the same issue.. the various Dev teams and other Apple support personal.. the problem was finally identified as an obscure bug in how OS X implements Thunderbolt.. (and was finally fixed very quietly in 10.8.3.) Had I not used a Case ID I don't believe for a second, that I would have obtained a fix for this issue because i would have had to start all over again, each time I submitted a bug report about this issue.. and there would be no documented history for Apple to refer to.
As for Ableton Live, I use the 64bit version of Live 9 ( as well as having used previous 32 (and more recently 64bit) versions for a long time now ) so I know it's little issues that affect certain users.. such as the long standing PDC bug... that still isn't properly fixed in 9.0.2... However, one of the positives of Live is it handles plugins much more efficiently than Logic does... but then again, it doesn't have anything like the same feature set as Logic as they are two different DAWs made for two entirely different workflows... so 'different horses for courses..'
Finally my comments about MBC were based on my own experiences with that plugin. As I said, each to the own but for me, I got rid of it some time back as there are much more efficent and better 'sounding' plugins of that same type, available these days... and of course, the whole 'stolen loops and samples' saga/mes that Vegeance are responsible for.... which is one reason I don't and will never support that company any further... and that personally, I think is dreadful behavior from such a company especially given their own restrictive licenses! (If you don't know what i am talking about, simply google "vengeance stolen samples" and read through a few of the results..)