I own a vBulletin site with about 10k posts, and I wanted to merge all those posts into a yaBB forum with 100k posts. Can you tell me how I could do this, or who i should ask?
You have to see which you prefer. If yyou prefer vBulletin, why go to YaBB. While we can help with YaBB to vB, the other way around would be YaBB's job.