@robshaw wile I’ve not owned either, and have studied your final two, there is another small yet mentionable factor to consider I’d think. Service, Repairs, where you live, and what’s around you for any reason you ever need to have them checked, re-biased, and while that’s not an issue usually - its not the first time these amps get sent back in (shipping cost two ways) and checked or repaired own down the road. They are built to last and that’s a good thing.
If you like to consider weight and current specs, maybe other things to ponder, and can validate this. I had to re-check a few times on the MC312 to confirm it. Also look at physical size too. Bottom line, you are the one that has to look at either. What inspires you more in how it looks [to you], big meters, in your room with your Fritz? Personally I think you’d be happy with either. Now splitting hairs a bit more.
The MC312 is 105 lbs weight unboxed, with 60 amps of current. [re-check this]
The Coda #8 is 62 lbs with 75amps of current. [re-check this]
Either will drive your Fritz fine [with grunt] and provide the extra body/weight you are looking for. You might even find you’ll mess with IC cables a bit too if one or the other amp is a bit too meaty in the lower/mid bass range. With wood floors in your room, hard to say. Make sure you can return either amp if you don’t like it for any reason. It’s worth ensuring you get an amp you’ll feel keeping long term and not looking back. Some don’t care and rotate many more amps, maybe find one you’ll keep and enjoy! ;)