Same Make or Mix-and-Match in a Stereo System?

From extensive reading of audio reviews, there seems to be opposing views on how to build up a stereo system. On the one hand, there are reviewers who argue that one should buy components from the same manufacturer. This, apparently, ensures consistency in the sonic signature and achieves the greatest synergy between amplifier and source. On the other hand, there are reviewers who recommend a mix-and-match approach, which involves buying components from different manufacturers that complement each other. Which approach will deliver the best results in terms of sound quality? (Apologies if this topic has already been dealt with).