The brand doesn't really matter in the sense that certainly the MSI & Sapphire will be fine together, just as the MSI & Asus or Asus & Sapphire would also be fine.
People just recommend brands they've had good experiences with, or what has better cooling and will survive overclocking and running 24x7 better, but this is all just based on peoples individual opinions. It would be hard to objectively tell them apart though because some people have really good experiences with one brand while others have the exact opposite experience, and so a lot of it is just hearsay.