14mm looks ridiculously small for the size of the watch.

14mm is awfully narrow for a full sized watch. Usually watches will only accept one strap width anyway. Are the straps that expensive? You could get both and swap between them depending on what style you like that day. Changing the strap makes the watch look quite a bit different.

Here’s a silly idea: cut out two strips of paper for the sizes in question, and wear them on your watch wrist. See which one feels better to you.

I'd get the 20mm