Mad, Mad, etc, is the older of the two. 1963 vs 1964, I think. Technically speaking, it was an effort to introduce the single-strip Cinerama format to replace the costly and cumbersome three-strip format with, while I think West was the last real Cinerama production (could have been the Grimm Brothers, though, but can't be arsed to check).
Thank you. Just as I was going to sleep it popped into my mind that is was Mad, Mad, Mad World. I was remembering "the Big W". Amazing what the mind does at 1:20 a.m.
I have a projectionist friend who considers Mad, Mad, etc to be the greatest movie ever made.
But then, we tend to rank films on their technical merits rather than details like plot.