Im not really sure what to think about the Leopard-1. Yes, it had great mobility, also good firepower. But that total neglect of armor... And its not just the protection-firepower-mobility triumvirate. For quite a long time, it didnt have a stabilizer, this somewhat negated its advantages in mobility. I have a soviet gunnery manual for T-62, and they acknowledge that the Leopard is very fast, but then strongly emphasize the lack of stabilizer, as an exploitable weakness. The night fighting ability of the Leopard until the PZB-200 was also quite deficient. At night, it actually had a 3 man crew, since the gunner didnt have any night sights, so he could do nothing at all. The commander now had to aim the gun, distracting him from his other duties. This is even worse than soviet tanks with their quite poor IR sights, where the commander at least could help with observation, at least for shorter ranges (~500m).
In my opinion, the Leopard was greatly inferior to the M-60A1. The american tank was slower, but actually had better cross country capability, had the best armor in the world until the appearance of the T-64 (fully 100mm APHE/APDS/APFSDS proof frontally). It also lacked stabilizer, but had much better night fighting ability. Probably it was also the best tank in the world in the 60s.