Quote Originally Posted by ian maybury View Post
I was brought up on both systems, and even worked for a couple of years way back as a machinist using both. There's situations where i'm much happier with mm (as in drawing/laying out work), and others where i'm more intuitive with inches.(household sized measurements and believe it or not thou based fits etc in engineering) Inch fractions i understand, but they really cause me problems in that other than very simple addition or whatever requires a pencil and paper.

What i'm maybe saying is that there's no definitive answer - that it's mostly a matetr of what we learn and become proficient enough in that it's intuitive. Trouble is as we get older it's harder to change/learn new stuff in the deeply embedded way we do when younger...
And that's the crux of the matter. As far as digital calipers, I do wish manufacturers would forego 1/128ths. I just have to move the head until I see a figure that is usable.