The courses are almost identical, with PADI's perhaps being slightly better (probably improved based on the SDI version being a good bit older). Someone not accepting the Self-Reliant card is likely either a PADI hater or clueless.Personally, I do not understand the difference in acceptance between SDI Solo and PADI Self Reliant. After diving solo for many years with operations who knew me, I took the SDI course in 2013 to facilitate diving with operators who did not know me. This strategy has worked perfectly well, with 100% acceptance of my SDI certification. Who knows what my experience would have been with the PADI certification.