Butane is non polar, so only non polar compounds like cannabinoids or terpenes readily dissolve in it.

Ethanol is amphiphilic (polar with a non polar tail) so it extracts the unwanted compounds (chlorophyll, waxes etc) too.

To add onto PiedPiper, ethanol is a 'harsher' removal method, so it strips away a bit more of that planty-goodness.

As I understand it though, the resin from both methods isn't safe to vape unless you completely purge the solvent. As it has a low boiling point (-0.5C), it does evaporate quickly, but can still be a bit of a bitch to get out completely. That, and it is also prone to go boom 💥

If you want simple, ethanol might still be better (with the caveat I have zero direct experience making resin, haha).

I'm no way a scientist but the same question rattled around my head a few years back, too. My thoughts:
RSO traditionally made with naphtha and even though it evaporates, maybe the idea of some solvent remaining behind put people off smoking it due to flammable, burns?

RSO known as "medical" and by not mentioning smoking, will fool anti-smoking/anti-cannabis puritans?

The evolution from RSO to FECO - I mean, I would think most RSO these days is made with alcohol? - would suggest to me you can smoke RSO.

RSO is maybe classed as full-spectrum nowadays but maybe it was once considered "dirty" because it contains not just cannabinoids but other plant matter, fats, oils, etc. and therefore not a pure extract. Trends seems to swing from full-spectrum to isolated compounds.

So, maybe it has been smokable all these years and the "oral only not for smoking" is just a perpetuated myth. Perhaps?

I see a lot of back and fourth about is it vapeable or not but if there both purged then there both basically the n the same boat and people are iffy and it’s kind of a rule that you can’t smoke rso

But people have no problems with smoking resin