Actually, ephedrine hcl is different than ephedra/ma-huang.
MaHuang is another name for ephedra. It is the whole herb containing many ephedra alkoloids including ephedrine, norephedrine (phenyproponalanine), psuedoephedrine, etc. It also contains other alkaloids, some toxic. Ephedra is a "dirty" thermogenic.
Ephedrine hcl is an alkaloid of ephedra. The most effective alkaloid in terms of beta-2 agonism; norephedrine is the best in terms of appetite supression.
(Tangental: I seem to remember that some ephedrine is converted to norephedrine in the brain, can anybody verify or debunk this?)
With ephedrine hcl, you don't get the negative effects of the other "dirty" alkaloids in ephedra. Similar to yohimbe vs. yohimbine hcl.