This is like asking people to choose between Gibson or Fender. Dunlop picks or...uhh...who else makes picks worth playing?
Seriously, this really is a personal preference thing. You mix on what you like the sound of, what helps you produce mixes that sound good on other systems. I was using passive JBLs with a Harmon-Kardon amp for years but found running the quiet my mixes all ended up massively bass heavy. I switched to powered KRK Rockits and things have improved a bit but I've still got a lot to learn when it comes to mixing. My mixing skills aren't being impeded yet by my gear, that's for sure.