I've never dipped into the Mark Series, but have a Tremoverb, Stiletto, Electradyne, Royal Atlantic, and TC 50 (and others but those are el84 based).
I used to run the Tremoverb and Stiletto together as my live rig because they compensated for each other's weak points.
Moved on to the Royal Atlantic and that's been the main rig for several years. Does the job of the two other amps for me in one head. Just recorded some demos with it a few weeks ago and remembered why. Lots of low end thud but still very good at cutting through.
The Electradyne is nice, but doesn't have as much gain as the RA and the shared EQ between channels can be challenging for using all three gain stages.
The TC50 is the newest one I've acquired and I haven't had a chance to try it in rehearsal/gigs, but I find it's sort of like a bit more refined RA. The separate EQ for each channel is great, and there is more gain available in each channel.
On the RA I typically use the red channel, on the TC50, I feel like the blue get's close to that and the red can be used for more when needed.
I really like the additional features on the TC, the midi control an rack mount format is great and I have it racked with a helix so I can get weird with it.