I haven't played either, but based on the amps architecture, they're pretty different. The Z is going to be lighter, brighter, and more chimey. The Runt will probably growl more; iit will be thicker and darker.
Difficult to really imagine two more different amps: $1500 price difference, hotrodded vox vs hotrodded fender (clean)/Marshall (dirt), 2 channel vs 1 channel
I’d choose the runt, just because I can’t really do single channel amps anymore. Or rather I don’t like doing single channel amps, unless they’re just clean pedal platforms. And I’m not paying $3200 to run a clean pedal platform.
Out of those two the Dr Z might be better suited. That said, between the prices of those two there are a ton of amps to choose from.
I tried the Friedman Runt 20, 50 and BE-50 Deluxe when I was shopping for an amp a few years back. I chose a Bogner Goldfinger 45 Superlead over all of them. Better master volume, better clean channel, more old school voicing. Just don't buy the combo, it's way too heavy to move around. Turned mine into a head and cab.