I cant really say for sure becasue I have never had black caapi. I have only tried yellow, cielo, white and red caapi. The only time I really felt much of a difference also was with the red caapi. I really really liked the red caapi, but I like all of them either way.
The higher harmaline content of black caapi is only somethign I have read others talk about and other places online, so I dont really know for sure..but based on reports of harmaline vs harmine it would make sense that black vine has more of it.
About the 3% in black caapi, it would be interesting to see some analysis on what exactly that 3% is entirely comprised of. From what I have read there is I think 9 actives found in caapi, though some might only exhibit background effects or have some mild syergistic activity. Alot of people seem to see that and think that that 3% must mean 3% harmine and THH with trace ammounts of harmaline, but I would bet that there are other alkaloids making up that 3%. Just as there are other alkaloids found in rue that would make the alkaloid % higher than what is found in a typical manske tek.
Also it would be interesting to see studies done side by side with caapi extractions and caapi brews so we could know exactly what dosage of caapi extracted alkaloids will parallel 50g or 100g etc in a brew.
My point is that, say 50mg of full spectrum caapi xtals might not be as strong as a straight mixture of harmine, THH and harmaline in the proper ratio at 50mg. There is just alot that we dont seem to know. This would also mean that the traditional data on harmala doses might not apply to a full spectrum caapi extraction, just as it would not to a full spectrum rue extraction.