It's not really fair in the Poll considering it's generational. Your 65-66 is relatively the same. 67-68 and 69-70 are also generations. Makes sense to do a vote by that than individual years.
I went 67-68. I'm not sure Ford will ever build a car that can match that design again. Not in how classic, nostalgic, forward, aggressive, and beautiful it is.
I've had every generation of fastback. In terms of driving, the 67-68's (coupe's and Fastbacks) are way more fun to drive. The 69/70's feel bigger and less nimble. The 65/66 cars ride like horse and buggies usually because they are so freaking lite.
While true, unlike today, you could easily tell what year the Mustang (or any car) was by looking at it since there was almost always something exclusive to that year only.