The sulphur lamps give off very little heat. NASA developed both the LED grow systems as well as the sulphur lamps so they could find indoor plant lights that give off little heat. It seems they have a problem in space losing heat inside the space craft once it's generated so they needed something more efficient than HID.

Either of them will grow cannabis no problem. There is a LED grow movie that I found but the director had just been arrested for creating it. I'm trying to get the company to post it on file transfer software so we could get it even though they obviously can't sell it any more. I saw some still shots from the movie though and they had some very definite fat ass buds. Will keep you posted.

The reason I believe sulphur lamps are better for large scale grows is that with all the extra PAR the difference in yield from one crop would make up for the cost of the light. Also, not having to compensate for the heat from the lamps would make up for a lot of savings as well, not to mention a better security profile.

Neither of the systems will burn your plants as they generate almost no heat. IMO, LED's would be for small scale closet growers and suphur lamps for commercial grows.