McClelland 40th Anniversary vs Christmas Cheers

I have puffed most of the Christmas Cheers, and have managed to accumulate tins of most of the vintages.  When the 40th emerged at the last Chicago Pipe Show, I stole a couple of flakes from Mary (with a wink, since they were now forbidden by the FDA to sell samples) and liked it so much I ordered up a bunch of tins.  The 40th strikes me as different from the CCs, being somehow lighter and sweeter.  Although the CCs can be sorted into flavor profiles, according to their genesis (various Belts, etc) and, of course, age, they all strike me as sharing an overall character in the realm of the late lamented 5100.  Keeping them in their original flake form when filling the bowl makes for a more nuanced delivery.

Anyway, does anyone have any ideas about compositional differences between the 40th and the CCs?  

hp
les