I started buying my own trains when I was in college in the 70’s when MPC was in it’s prime. Trainworld opened a store on Avenue M in Brooklyn, right next to the subway stop I used to use going to school and work… and my feet were “firmly” planted on the slippery slope 
MPC offered a more colorful and varied line when compared to most post war offerings. The standard O offerings were eye opening - larger, more realistic, and in some cases, cars not offered in the post war era. While I don’t run them anymore (I’m a command control-a-holic!!!) I still have and treasure a number of MPC engines. If you run conventional, I would certainly recommend the MPC era engines. Regardless of how you run, many MPC cars are worth having on your roster. And finally, in the 70’s and 80’s, Lionel made a number of 15” aluminum passenger cars which were excellent and look great on smaller layouts.
