Krell can be forward and thinned out on top.. mcintosh a bit more Solid state with tube sound.. Krell depending on the speakers will have authority to really have tight punchy bass, but mcintosh has a low damping factor that works well with easier to drive speakers making them sound a little more vast, organic, or natural in the bass.. Sometimes this can with some speakers seem as a little more "Full"...
It will also ultimately depend on the impeadance match of not only the speaker to amp, but the preamp or source driving the amp as a synergy match.. I think if you want more detailed and sometimes "spacial" sound the Krell will fit that bill, if you want a little more intimate feel or "Warmth" in sound the mcintosh normally tilts that way.
Unfortunatley without playing them both in your system and seeing which way you tilt, it will not matter. so in the end no answer will be satisfying let the accusations fly!!
As for facts on ownership they are both huge names in the business, both will have equal fans and foes, however in a general "Used" market mcintosh has one of the highest holding values still for electronics, and does not have as high of depreciation that most gear carries.
