Thomas R. answered 06/23/19
Over 25 years of experience and a sense of humor about math
I never really followed the ceremonies -- just as I ignore most awards or award shows -- but this question sparked my curiosity.
It turns out that one is official, the other unofficial. The Nobel Banquet is held by the Nobel Assembly, an official division of the Nobel Foundation. It honors the newest winners.The Nobel Anniversary Dinner, on the other hand, was founded by Albert Einstein to honor past winners, living or dead. However, the latter ceremony seems to have fallen into disrepute, and its website is loaded with sports scores,according to the sources I found.