[Zamicol]

I'm not confident of the math there.

https://i.imgur.com/cAVbqka.png

Because of quirks, in edge cases decimal is more efficient, but overall alphanumeric is better in QR code.

[komlan]

Ah, I was assuming numeric data rendered as hex, like UUIDs. Decimal works wonders for those, because the numeric mode of QR codes is the most efficient.