I take it the 'know exactly what he/she is taking' is meant to say 'how much he/she is taking' since a measured amount of a powder could never be more than 100% pure so the dose could never be higher than the exact same quantity you weighed.
We don't do 'what should I get?' threads here, please make up your own mind.
Just like with MDMA some people like crystal better and others like pills - that contain it obviously - better. The difference is in kinetics (Not to bore you with matters like peak plasma levels, but it can just be a bit different.) : crystal or powder may hit faster but smoother as it is gradually absorbed while pills - entirely depending on the binders and how hard they are - can sometimes hit more suddenly. One is not really better than the other, but people can have preferences based on pro's and cons, including what lama-cowgirl suggested as advantage.To each their own.