I agree with heypaul. I was a teenager in the 70's and got my first tastes of railfanning back then. On the positive side, there was a much larger variety of rolling stock -- BMT/IND running both R 1-9 AND R-44/46 equipment (when it the 44's were working); as well there was the R-40 (slant and modifieds), the 42s, the R-27/30 workhorses and even the R-11/34 experimental cars that were holding down the Franklin Avenue Shuttle.
Negatively, however, the system in general was in a state of decline, with both horrendeous graffiti and deferred maintenance problems. Also, subway crimes were at out-of-control levels.
The best aspect of that era was certainly the diversity of equipment, much of them never to be seen in service again.
Doug aka BMTman