RF SCs are stronger than purilum (I'm sure there are exceptions). But the purilum flavors are very good.** Better than a lot of tpa/cap flavors, on par with a lot of fa, just slightly weaker than fa (again, with exceptions). If yyou'e trying to reduce pg, then obvs the SCs win. Otherwise I think they both have their place. It's hard to pick one that is my favorite, but purilum has really nailed a few that I will most definitely be keeping in my rotation. The SCs are wonderful but I'm still trying to get used to them. They seem a bit trickier to pin point the exact %, but once you do they really are delicious. Of course once people start making/publishing more SC recipes, it'll be easier to get ideas of %s that work well.
**I should clarify, not all of them have been wonderful. But I've tried a lot more good than bad. Your tastes may vary, but I do recommend trying both of them.