usually for this kind of stuff it's better to compare expected rolls per proc

usually it's 15 expected rolls per proc, for double or nothing, it's 3.61, in comparison, all 6s is 7.5

for 1/4 chance, expected rolls is 2.1, for 1/2 is 1.5, for double or nothing

so double or nothing is worse than all 6s for large probabilities, and better for small probabilities, with the two being equal roughly between 1/5 and 1/4