Hi there jadugar,
My understanding is that the XP60 and 80 are identical in every feature except for the lenght of the keyboard.
If true (and I think it is) then you will be paying the additional money only for a handful of extra notes. Whether it's worth that, or whether you can manage with a slightly shorter keyboard, only you can decide!
I must say I love my XP-60, and if there is decay noise I've never noticed it.
The otcave shift up/down keys easily compensate for a few less keys for my purposes. It all depends what kind of player you are I guess.
All the best,
Martin