It is very hard to be objective on such claims due to:
- it is hard to quantify 'danger to health'
- objectivity of research (or lack of, due to funding that favors certain results by certain groups)
If you examine wikipedia's article on MDMA (ecstasy) you will find this image that comes from The Lancet, a weekly peer-reviewed medical journal:
The original paper from which the image is taken is: Development of a rational scale to assess the harm of drugs of potential misuse.
It supports the claim that MDMA is less dangerous (with much lower dependence and slightly lower physical harm).
However, do not generalize, you should examine the test in details, for example:
- does test take into account problems with purity (uncontrolled substances can be mixed with scary things)
- does it measure problems with dosage (very high, difference can be two orders of magnitude, which easily leads to accidental overdose)
- how were long term effects taken into account
- comparability of data quality
Finally, the danger is also subjective, here is a quote
It found that the likelihood of a newspaper reporting a death from paracetamol (unclassified) was one in 250 deaths. For diazepam (Class C), it was one in 50. For amphetamine (Class B), it was one in three.
For ecstasy (Class A), every associated death was reported. And I very rarely read reports in the national press about those deaths from horse-riding accidents.
I recommend reading the whole article.