This should probably (heh) like be in the probability forum, but I'm curious anyhow.

This is a BR stats type of question (risk of ruin) that I basically have no clue about. I think the ROR is greater for the 2nd option (quadruple up) is higher because the SD is bigger. We would expect to go bust 3/4 times. Now if we do the former (double double), we expect to go bust 1/2 times on the first bet. When we don't go bust, we have the same shot at going bust 1/2. Bah, see, I really have no clue actually.....