Physically, it has no bearing. However, mentally it confirms the addictive behavior. Because of Sub's long half life, there's no reason for twice a day dosing...and, sitting there dosing to keep away withdrawals or to get a "lift" is only telling you addiction that this drug is no different from other opiates. So, that's why doctors with significant addiction experience (not just a general GP) suggest once a day dosing.
I know people who do both, I don't think its any worse to take the subs twice a day but I have heard that from a lot people that are on it that the lower the dose they take the better they feel, talking about feeling normal anyways. Most of the people I know start out taking it twice a day and then after several months they only take 8mg once a day and then 4mg and so on until they are done with it.