That arrangement is primes. The other arrangement is sevens: 1 and 6 opposite each other, 2 and 5, and 3 and 4.
Both of them can be unfair. Assuming rolling high is better, when 1 and 2 are opposite each other, those faces could be slightly smaller and therefore have a smaller chance of landing on them. This is especially easy with hand-made dice, which are bound to be somewhat irregular.
With "sevens", 1, 2, and 3 meet in a single point. If that point is somehow heavier than the opposite point, you're more likely to roll 4, 5 or 6.
I think I'd actually consider the "primes" arrangement to be superior to the modern one. No idea why that switch was ever made.
Both of them can be unfair. Assuming rolling high is better, when 1 and 2 are opposite each other, those faces could be slightly smaller and therefore have a smaller chance of landing on them. This is especially easy with hand-made dice, which are bound to be somewhat irregular.
With "sevens", 1, 2, and 3 meet in a single point. If that point is somehow heavier than the opposite point, you're more likely to roll 4, 5 or 6.
I think I'd actually consider the "primes" arrangement to be superior to the modern one. No idea why that switch was ever made.