When I worked in a machine shop it was the classic use the right tool for the right job. And if a measurement didnt need a 6" caliper then you didnt use a 6" caliper. Now, of course, I realize this is overkill. But I did run into situations where the length of the caliper was an issue with the measurement in some tight spaces. It was far and few between, and I probably would not encounter such a situation working on cars, but the principle was there with me when I was shopping and the prices were good so I figured why not. To be honest, the next time I am there I may pick up a 8" caliper as well.
Again, I know its overkill and I may never encounter a situation in which having a caliper that is too big will be an issue, but with the prices I didnt see any harm in being prepared.
