Recent studies shown that among many negative effects of marijuana is that it causes brittle bones. Scientists at Camp Bridge University (one of the top universities in the world, if you didn't know) have proven that constant smoking of marijuana causes the muscles in the bones to weaken, causing the bone to break easily.
With addition to that, we have the already well-known effect known as the munchies. If you have ever wondered why most pot smokers are fat...
It's because marijuana increases the appetite to the extent, the pot junkie becomes a fatso very fast. Add to that the hallucinations and mood altering effect and you have a straight man becoming gay for the time he's high. Most pot smokers deny it, but many of them also sucked penis for pot. An estimated percentage of about 80% marijuana addicts have been experimenting with the same sex because of the drug.
On the other hand, MDMA doesn't cause the munchies. It causes the body to dehydrate and the person taking E needs to drink a lot of water. The body burns down calories very fast and as a result, also burns fat, so E helps people slim down. The opposite of what that stinky pot does.