Dave Grohl and the Foo Fighters were the best things to come out of Nirvana, and I like Nirvana
Nirvana undoubtedly had a larger impact culturally and financially, but the Foo's made better music, Kurt dying unfortunately resulted in Dave's musical evolution, Dave had been in several bands prior to Nirvana (playing all sorts of genres) and Nirvana gave him the means to do his own thing and really run with it
One could point to record sales, but one could also point to Nirvana booming at a time when physical sales were still a mainstream factor
One could also argue Nirvana didn't get a chance at longevity, and while that's true it also is what it is
One could also argue that Foo Fighters may have still happened even if Cobain hadn't died, but we'll never truly know
Kurt was undoubtedly the epitome of grunge and is a defining character from that era, but Grohl is undoubtedly the better musician, better voice too imo
It's weird how it worked out, Kurt never wanted to be a rock star, Dave is one of the world's premier rock stars, to the extent that he's known as the nicest guy in rock