I've quoted an excerpt from Lebot's book before, that shows how convoluted the language gets with the names.
In short, there are over 100 different languages spread throughout the Vanuatu islands, and the Borogu/Boroguru/Borogoru/borongoru etc. names can change from one island to another and even from one part of an island to another. it's also known that the same cultivar can produce different strengths and chemotypes to some degree depending on how and where it's grown...so it gives a lot of leeway...
that being said, i think the modern consensus is that Boroguru types are heavier and more sedating and Borogu is more balanced and leans to the heady side, while not being completely heady.
I think they might all technically the same cultivar, but there are definitely some places growing a 'medicinal' level boroguru plant with a 245xxx-ish chemotype that seems to typify what we've come to consider as "boroguru".