None of them are really worth it. You certainly don't need to use them as often as they recommend (if it's not broken, don't fix it). But if your car is running crappy give it a try. It certainly won't make it worse. As for which one is better, I couldn't really tell you. I always went for the ones that claimed to do the most (and thus cost more). But I've never used any of that stuff on my RS.