Don't own a Mark V but do have a Mark IV. But there are a few guys here who own both and a couple that sold there Mark V's to get ED's (As I am certian there are guys that sold there ED to get Mark V)
I have been getting the urge to pickup a Mark V as well, but I would give up the Mark IV as the ED fills a different niche.
I will say this. I had the opportunity to play an ED combo and a Mark V combo side by side, and for overall thickness, the two amps were not comparable. The ED just has a much fatter, thick rounded tone.
But two weeks ago they had a Mark V hooked up to a 4x12 and I got to spend some quality time with it and for the first time I was able to get some really great tones out of channel 3. I was always able to get great tones out of channels 1 and 2, but channel 3 I had yet to get anything out of it that could compare to the Mark IV. But I still didn't think it sounded quite as thick as the Mark IV.
Now the Mark IV is not as thick and rounded as the ED either, but the difference isn't as big as what I experienced on the Mark V I tried.
I need to save up another 200-300$, but after that I am going to bring my Mark IV in along with my recto 1x12 cab and see if they will let me AB the Mark V and Mark IV. Hopefully the Mark V doesn't require a 4x12 to sound full. The Mark IV definitely doesn't.
I already know the EQ on the V does not compare to the EQ on the IV. The EQ on the IV is much more responsive.
But if I can get the same or better quality out of channel 3 on the Mark V that I get out of the lead channel on the Mark IV, I will probably go ahead and sell my Mark IV to pick up the V. But that is a BIG if. I have a strong suspician that when I side by side them the Mark V channel 3 will sound thinner then the Mark IV lead channel. And if that is the case the Mark IV stays!