There are a few stereotypical nasty zones on most MkIIIs that you learn to avoid. Most if them involve, a.) the ice pick, b.) the mud zone, and c.) flub. Speakers play a huge part in where those areas lie, but because the tone controls are so flexible, they are there in a big way. The bass control is usually WAY too influential on a 1x12 combo, especially the EV12L. But it can round out thin sounding speaker cabs, too. Not everyone uses the combo speaker exclusively, so obviously, YMMV.
Most of the polarized opinions come for those that believe every MkIII sounds the same, reacts the same, uses the exact same speakers, and are only playing Metallica and Dream Theater covers. :lol: Don't sweat it and enjoy your MkIII. 8)