It's interesting to see how the scene's assessment of Burzum and Mayhem has shifted over time. In the mid and late 1990s, there was a definite tendency among those metal fans who enjoyed black metal (still in those days a distinct minority) to prefer Mayhem to Burzum. These days, that preference is Burzum. To some degree, I think this is because Burzum's music is simply better, but took more time for people to really process. And there was that whole murder/arson/jail thingy.
Still, I wonder if Mayhem's higher profile in the 1990s also reflects the demographic shift in the black metal audience since that time. The bulk of the (knowledgeable) fans in those days were definitely more like an old school "heavy metal" crowd, basically more blue collar, and their listening history was pretty much exclusively metal, unless they had a smattering of interest in grind and hardcore. The audience now skews more middle/upper middle class, white collar (IT guys wanna go analog sometimes, too), and way more likely to have something in their listening history other than metal. Burzum's basic sound is less rooted in traditional metal technique, and by Hvis lyset tar oss and Filosofem, there was almost as much convergence with ambient music, darker dream pop (Dead Can Dance?) and even shoegaze as there was with metal (although I suspect the dream pop and shoegaze similarities are examples of parallel evolution rather than direct influence). Mayhem, on the other hand, was always the Norwegian band most like the metal that preceded it.