That's kinda impossible to say... they were from really different periods of time regarding music (for example, when BOMT was released, piracy was not so consistent, people used to buy more albums and Internet wasn't as used as it is nowadays).
I'll give Beyonce My vote this time. BOMT is to overrated. Sure it was a big bubble gum song for the Teens, but over all, Single Ladies was Much Bigger, i mean the Dance Alone>>>>BOMT. It gave teens their songs, but i dont see how much it had influences and an impact. Single Ladies not only had an ICONIC, yes im using the word correctly because i am using the word correctly now, Dance, but it had a Memmorable Video, which was ALL OVER the news. Everyone was dancing to the Choreo, uploading on youtube. It even was remembered by glee, and Our sistren Joe Jonas bopped and covered it. Single ladies is TRUELY underrated. It had a MAJOR impact on music Culture.