Purer yes, not stronger, because MDMA is MDMA, not like Marijuana where one batch is more potent than the next. His level of purity would be one of the highest though, along with other labs.
IDK I bet his MDMA would give you a lot more empathy than even 100% pure MDMA made by others. Just seems like he would have a lot of experience, and with trial and error he could refine his MDMA synthesis so it would give a better roll while still being the same chemical.