I personally love the 1971-73 Buick “Boat Tail” Rivieras. Buick just always had a flare for making the Riv just different enough to make it desirable but they really went over the top on these three model years.
I have noticed there seem to be three different levels of desirability for these cars depending on its year.
First, at the top of the heap is the 1971. It seems to be in this spot due to its having the closely cropped bumpers front and rear AND those beautiful louvers on top of the trunk lid. I love those too and if I were in the market for a Boat Tail, I would definitely make a special effort to locate one of the '71s.
Secondly, and bucking the tradition of the last of a three-year production run being the most valued and desired, is the 1972. I believe they are next in line because they have the closely-cropped bumpers front and rear but do NOT have those gorgeous louvers of the '71s.
And then trailing in third place seems to be the '73. It seems to be well behind due to not having louvers but mostly because it has that incredibly ugly government-mandated front bumper along with the usual bumper on the rear. But it takes a lot to get over '73 front bumper and as such their desirability seems to be based accordingly.
These are merely my observations but I feel they are spot on. I’m not particularly a Buick fan. I like lots of different kinds of cars. I just appreciate beauty in a car no matter its origin. In fact, I LOVE the 1970 Rivieras because they really are a one-year model. And boy do I love those fender skirts on the '70s!