Again, read that post in which I tagged you and think deeply and then compare...
Whatever points you said exist for BB as well.
But whatever point I said for BB does that exist for Buggy?
Not really the only person in black beards crew that ever defeated any straw hat is Kuzan and it's still up in the air if he's 100% loyal
Blackbeard hasn't fought, argued or reluctantly teamed up with Luffy at all
In fact they only met twice
First when they talked about pies and then again in Impel down where that fight was cut short by jimbe holding Luffy back
Now let's go through your comparisons
Both Ds ? Multiple people are Ds, Laws a D does that mean he's the most important rival to Luffy?
Light vs Darkness? Yeah fair point but Luffy is the dawn and the reincarnation of the guy who fought the world government in the firts place so Luffy light and bringing the dawn is more describing him being nika and his clash with the world government, Black Beard is the Darkness that Koby will take out
Roger vs Xebec? We don't know how that fight went at all for all we know Garp could have been the one to take Xebec and if anything Shanks and Black Beard are more the Roger and Xebec of the current era
Polar Personality- Buggy and Luffy have pretty polarizing personalities that give similar results
Polar Ideology- having different view points doesn't make you a rival, most pirates in the series share Black beards Ideology, Luffy is the odd man out
Common Goal? - 99% of pirates in one piece have the common goal of becoming pirate king
Similar crew structure? Are you referring to how they both have 10 core members fair enough Cross guild only have 9 rn unless you count the guy who killed T-bone but even if you don't they have Buggy, Mihawk, Crocodile, alvida, Mr 1, Mr 3. Richest, moji and cabaja and could possibly recruit moriah to fill out that 10th spot
We don't know Buggys dream beyond the one piece but I'm sure he has one