Earl had a lot of reasons to switch... there were minor sonic benefits, but it was more than that. The original cabinets took a lot of effort to build and also were damaged in shipping quite a bit (the new ones have been more than he expected too, it seems). The newer cabinets may look a bit nicer and also have the woofer to be mounted differently so the screws aren't visible, that's the nicest thing about them IMHO.
The cabinets he built in 2009 were fantastic, though. I have a pair...they're very solid. I've done everything in my power to avoid selling my pair of Abbeys and for good reason. Need 130 db peaks? CD? Efficiency? Great SQ? All there.