Metric sizes of bolts/nuts are inferior to the Whitworth equivalents=20 because of the shape of metric tread with the sharp 60=B0 angles which a=20 big stress inducer.
The remarks about the availability of "fine" metric treads are correct=20 too.
Metric is imho a system based on mathematics, allowing easy counting. It=20 is however not based Nature: there is no such thing as a "natural" meter=20 but everybody has feet and thumbs (inches). It carries through on speeds=20 and distances: a nautical mile has a rather straightforward relation to=20 the Earth diameter, a knot is one NM/Hr etc.
The fact that metrical has no relation to Nature is imho a major=20 weakness in the system, the second weakness is that the metrical system=20 carries on with areas where it is not applied: charts, time,=20 yearcounting, so it always stays a mix.
Tom De Moor