Which model year is the least desirable for you, and which one is the favorite in your opinion?

Least desireable is a '76 (even tho i own a '75)
and the most desireable is a '71. I dno why. Just because.

as it was the latest year with round taillights, and '76 was good as it was the last year and BMW had the "bugs" out by then (and the 3.91 diff).
'75 has been dogged as it had the thermal reactor and more-readily-deteriorating rear seat Gummi-haar.
I've enjoyed my '70, '76 and the current '74 tii. Just get the most solid one you can afford, regardless of the year.