Correct. The XXL does have different bevel gears in the transmission also. It provides a lower reduction(faster tranny). However, depending on your powerplant, you might not need them. The new LST conversion kit comes with a new bevel gear set as well, lowering the reduction again(faster tranny). And of course on all transmissions, you can do the swap mod for a slightly lower reduction as well.
Otherwise, parts are pretty much the same. Shock bodies went back to plastic threaded bodies. And I think they change the steering servos.
Fantastic work man ... I love the carbon chassis plate with the aluminum inlay... sweet.... I am also just loving the attention to detail through out your build... every piece is so well done.