Charlie,
I think the US switched to the bigger ball eons ago because on the generally lusher fairways the small ball didn't sit up as well as the bigger ball.
If that's right, it was long before Jack Nicklaus was even thought of!
Tom,
The first 1.68' Open was at Lytham in 1974 - so Watson never played a 'small ball' Open.
Not having to switch balls -and having to learn to play with the more difficult to hit 1.68' ball- was unquestionably a factor in the almost immediate emergence to the superstar generation of European players - Seve, Faldo, Langer, Lyle, Woosnam, Olazabal. Monty even:)
The US switched to the big ball in 1930. We also dropped the weight to 1.55 ounces, resulting in the "Balloon Ball." John VdB has an excellent essay on it here,
https://golfclubatlas.com/in-my-opinion/john-vander-borght-the-balloon-ball/That said, I have contended for years that with today's manufacturers have shown their ability to control spin, launch, etc. simply reducing the maximum weight of the ball would accomplish most of what people seem to want. No need to go to 1.55 ounces, however.
I would make the ball curve more and make it more susceptible to the wind, especially at high ball speeds.
The other thing is that it would reduce the ballistic coefficient of the ball, meaning that the faster it launched, the more speed it would lose in the first 50 to 100 yards. As it lost speed, or if it was launched at a lower speed, the effect becomes smaller.
So, it would have almost no effect on the shortest hitters, except in high headwinds, and it would be easier for them to keep the ball in the air.
It would sit up a tiny bit better on the grass, which , again, would be more benefit to the weakest players like seniors, women and juniors.
But despite Callaway making a ball that embodies the idea in the Reva, which isn't lighter, but bigger, 1.73 (vs. 1.68, while the "small ball" was 1.62). It's based on the Topflite Magna that Callaway got when it bought the brand.
I'm in the shortest hitter camp, and have played the Magna and Reva a bit. They do work, but I like balls with a little more greenside spin.