Peter,

Don't know for sure other than the folks with the older airplane do a
lot of the work themselves under the supervision of their mechanic and
its fuel burn is less; plus they haven't had too many avionic problems.
I keep hearing the others bemoaning various and sundry ills, fuel
controllers, avionics, just unsceduled maintenance to the tune of $500
or so each month.

All the best,
Rick