I think that long term damage is far more important than the effects of the drug whilst in use. When heroin addicts die, they no longer disturb anyone, nor do they use government resources (or our taxes). Casual ecstasy users are going to have on going problems that may not even show for 7 - 10 years. The next generation with their delayed out break of mental and physiological illnesses is already being deemed as an "epidemic" for the next 5 - 15 years. The resources on the government providing for these users and their delayed problems will be far more taxing then throwing a few bodies into cardboard boxes.
Beside that, the question is the actual drug far more dangerous on our brains, and the answer is yes.
MDMA effects the serotonin levels in our brain, a chemical which is already naturally produced and is responsible for controlling moods. It is proven that if you are a heavy user, and by health professionals that is more than 50 tablets in a LIFETIME, that your receptors in your brain which transmit signals of how happy/sad you should be feeling are permanently damaged. When these are damaged, obstructed and even completely destroyed, you are left with a person who is prone to paranoia, impulsivity, aggression and of course depression, just to name a few. These are long term effects. This is because MDMA is neurotoxic, something that heroin is not. Heroin does not destroy neurons in your brain therefore heroin does not cause any long term damage. The only consequence of long term heroin use once rehabilitated is always having the 'taste' for it.
Also I would be careful using the term 'Designer Drug' Ecstasy is no way a designer drug, a designer drug is a drug which has been derived from a legal substance.
Feel free to correct me
Thank you and have a nice day:D