No idea if they different spec other than being fitted with Air Conditioning, which isn't fitted to the Worcester examples.
It should be noted that on Thursday it didn't struggle on any of the hills, as noted by "Red Midland" who was a passenger on a few journeys that day, yet by Saturday it had become notably slower on the hills and even on the flats.
In Leicester they only ever run around the City and I guess running mostly flat-out between Worcester, Hereford and Hay continuously for 3-day took it's toll.
PS, thanks for the can of pop!