you could argue metric is objectively more rational given that it standardises conversion factors between different size units, and makes those conversion factors into powers of 10, which matches nicely with our number system. it also has superior convenience for converting between units of different dimensions.

that said, there's nothing objectively better about the actual individual metric units themselves. a metre is no better than a foot for measuring length. a litre is no better than an ounce. even having the numbers match with our number system doesn't have to be unique to metric, since you could easily design a similar system using feet, milli-feet, kilo-feet and so on.

where the metric system objectively outperforms is in converting between units.

1 litre of volume is 1 cubic metre. taking the base unit of length and cubing it gives you the base unit of volume. it's all neat and fits together, and the numbers still line up with the base-ten counting system. doing the same with imperial, 1 cubic foot is 996.614 fluid ounces (standard imperial, not US), which is not as neat nor easy to remember nor easy to work with mathematically.