hI,
here are my thoughts in a nutschell as I owned a MK V and still own a IV.
Mark V:
Ch 1 : awesome, unbelievable, maybe the best clean ever
Ch 2 : all the modes are very nice, the MK I mod is great, big dark grainy rock tone.
Ch3 : C+ mode : i never managed to approximate the real C+ tone
IV : interesting, focused, beefy and some nice modern elements
Extr : definitely modern, tweakable, focused
Mark IV :
Ch 1 : sparkling, warm , very nice
Ch 2 : i never managed to tweak an interesting tone, compatible with my playing
Ch 3 : tweakable, warm, creamy, focused , perfect for searing leads
Bottom line :
I sold back the MK V, kept cautiously the MK IV and bought a third MK IIC+ because after playing the V, I was definitely convinced that it's impossible to replicate the C+ benchmark tone. :lol: