One thing about Ephedrine and caffeine is your beta-2 receptors won't become overstimulated, which can happen with clen, and is why it is a wise decision, should you choose to use it, to use it only for a brief period followed by a period off. You'll also want to use something like benadryl or ketofen after the two week cycle of clen to help upregulate the receptors.
For some, clen can make them really jittery, so ephedrine is a better option in this case.