The metric system has a more rational basis, rather than a guesstimate of the length of some ruler’s thumb several centuries ago or the packaging habits of mediaeval farmers.
Multiplying and dividing by powers of two and three made sense when almost all measuring was done by eyeball, but it’s not well-suited for precise measurements or large numbers. We have a decimal numbering system, so a decimal system of measurement is a no-brainer.
It also makes all sorts of calculations easier. For example: How many gallons in a cubic foot of water? Time to bust out the calculator (for the record, 7.4805195). How many liters in a cubic meter? 1 million cc = 1000 liters. Top-of-the-head math. It’s not just a coincidence that physics, medicine and chemistry settled on SI units a long time ago.
I believe that the metric system is superior, and that there’s not much debate about it. That leaves two other questions: 1) Whether it should be imposed on commerce by the government, and 2) whether it should be imposed by treaty on one country by an international body.
The answer to 1 is yes, to at least some degree. The government has to maintain standard weights and measures if it is going to even attempt to prohibit unfair trade. You can’t have each seller defining “ounce” his own way.
The answer to 2 is a little bit trickier. International trade requires standard measures, just as domestic trade does. But since acreage is neither imported nor exported, is its measurement really a matter of the EU’s concern?
So, which makes more sense to you, the length of some ruler’s thumb (which is probably pretty close to the length of the thumb located at the end of your arm), or 1/10,000,000 the distance from the pole to the equator, as it passes through Paris, France? Having never walked from the pole to the equator, I have no idea how far that is, much less 1/10,000,000th of that distance. But as the possessor of two M1/A1 Mod0 thumbs, I know pretty much how big they are.
For some things, SI is better, and it already predominates in these areas. Ask a chemist to do something in ounces or cups, and you will be greeted with a blank stare. But for the majority of things for the majority of people every day, it has no great advantage.
I take a modified libertarian view. Measures must be standardized, but people should be allowed to use whatever standardized measure they want. In the US, this will mean that English measures will continue to be used for a long time to come for most things, while certain technical trades will go their own way.