I've seen BK sold as Molly pretty often at festivals, as it's cheaper and a lot of people (example: average concert goer) can't seem to tell the difference (but these are the same people who buy clearly fake pressed pills from sketchy gang members roaming the crowds).
Personally I like BK, but I wouldn't choose to use it if quality MDMA was available, as it is weaker and not as intense. If you get the dose right it can be really similar to Ecstasy, but if you've rolled enough you can spot the difference. One thing is for sure though: it is very moreish. Typically after a good roll, you don't have a huge urge to redose, but that is not the case with BK.
I disagree with it being "healthier" for you though. Drugs are drugs.