A Nikon or Canon DSLR with a decent wide-tele zoom will be more than adequate for producing excellent quality calendar-sized images. Frankly, even if somebody could prove to me that the MF film images would be superior in some way -- and I doubt they could -- it would certainly be an insignificant difference at typical calendar size images. So I think you can quality at worst case, equal... Now compare the film workflow to the digital workflow, and digital will win hands-down.
For sure, the old Hassy's are beautifully made pieces of machinery, so I understand the nostalgia around owning and using one -- kind of like driving an antique or classic car. So if that is going to give you a certain pleasure over shooting with a space-age plastic and metal electronic marvel with lots of buttons, then that is a valid consideration IMO. But the Hassy itself won't necessarily mean "better" images at the end of the day, and in fact will most likely mean fewer images total...
My .02,