I believe the next batch of RM cabs have had an upgrade, which will be present in the new combo and new kit going forward, not sure about the OriginAL heads though, but it kind of muddies the water however as they look the same, I expect any good deals coming out of the big retailers will likely be old stock.
They seem to nip and tuck as they go along in batches of production, I'd always advocate buying direct and talking to the guys at Ashdown which would make sure you're getting the best kit, they're really friendly and helpful too.
The combo has one edge over the separates, and that's the ability to lean the cabs back from monitoring purposes. I guess it's not going to be a deal breaker for everyone, but I would certainly found it useful, or certainly would've when I gigged loads pre kids...
Eude