A repetitive dive is any dive that occurs before off-gassing of nitrogen has completed. This time will vary depending on the dive, and the dive table used. US Navy Dive tables give a maximum length of time for this to occur as 12 hours, while NAUI dive tables put it at 24 hours. Under PADI tables you only have 6 hours to off gas completely. When in doubt being conservative does not hurt but pushing the boundaries certainly can.
For comparison purposes, a side-by-side exam will easily show U.S.Navy Dive Tables to be the 'safest', or most conservative, giving the longest decompression /out gas times, next safest are the (sadly) now-defunct NAUI tables, which are only slightly less 'safe', or conservative, while the resort/hotel/rental industry-sponsored PADI 'tables' are simply designed to let a diver belt down a couple more beer on the 'safety' boat before diving again.Answer
As far as what is most conservative, it depends on the profile. For a single dive, the U.S. Navy is not the most conservative. But for repetitive dives, it can be more conservative. The question should be simplified to what is the time needed before previous dives do not need to be considered. For some mild moderate dives, PADI's 6 hour surface interval with the RDP works very well. But if many dives are being made, then 6 hours may not be long enough to be considered "clean."