I own both, and I love both! Both amps offer great clean, low gain/crunch and hi gain sounds which are seamlessly footswitchable. The ED offers great sounds in each mode, but there are some definite compromises between modes for gigging by the nature of the intentional "simplicity" of this amp. That being said, I can easily set up the ED to cover the essential clean, crunch and high gain sounds that I need for live performances without much sacrifice.
That being said, my preference is definitely the MKV because with this amp each channel has 3 modes (most of which I love), each channel has dedicated tone and presence controls, power mode selections, Graphic EQ choises, reverb mix levels, etc....and all necessary functions are footswitchable. The MkV also includes the very useful footswitchable solo boost feature which was not available with the previous Mark amplifiers.
I know this is the ED forum, and don't get me wrong....The ED is an excellent amplifier and for many may be exactly what they want / need. However, for me the MKV definitely rules. I am not just comparing it to the ED, The MKV is the best amp for me period!