Well, SSR1 has light abrasives in it, so that would make it slightly more agressive than PWC which is strictly a chemical polish (at least to my knowledge). Personally, I use SSR1 when I am going to top it with a sealant and PWC when I will use a natural wax. I just feel that its better to put a sealant directly on the paint as sealants sometimes don't bond well to carnauba. However, many people on DC use PWC under everything and overall I would say it is a more popular choice than SSR1. Both are great products though, try them out and see what works for you, you cant go wrong with either.