In Stock, and Super Stock, the 69 has the widest variety of options for engines and transmissions. Anything from a 250 6 cylinder to a 427. You can't run the 427 in a 67, 68, or 70. You can't run a 396/375 in a 67 or 68 unless it is a 4 speed. The 69 Camaro probably fits more classes within Stock and Super Stock than just about any other car.
I'm not a huge fan, but the guy who owns the car is. I'm probably going to build a 69 Chevelle, I like them better.