What I don't like about metric is when you actually have to build something. Between number, Letter, and Fractional drills, the increments are in .0001"s 10th's of a thousandths of a inch. There are so many more thread sizes, you will never find machine size threads in metric, as in hi-tech sewing machines, which is why American SAE will never gone. Metric has been absorbed and any machinist or mechanic worth his salt has tooling for both, but what you can do in SAE you cannot do in Metric. It is easier though, and for certain applications, it may be better, such as space travel, and similarly related measurements.
Yes, metric scales up easier, when making these models though, biological objects will never be the same size, so both systems go out the window. You have to design on a "mean", and decide how much you will vary from it.