Clen gives a slight edge. If you don't alter diet, it won't bring noticeable results. Diet and cardio are the foundation, clen will improve those results. You'll feel like a jittery Crack head on it regardless. I'm not a huge fan and only have used low doses.
Something like DNP will give noticeable results even when diet isn't as tight. It's really quite silly how easy DNP makes it. People generally hesitate to proclaim this openly and publicly because lazy idiots will go out and try it and potentially hurt themselves. But you have to be a genuine retard to fuck DNP dosing up. Just keeping it real.