I never do matching appliances so probably not much help but if you already had a SZ and loved it why not go with what you know.

Are you planning to panel it? Then just look for the one you like best. You definitely don’t need to match them if it will be paneled. The only time matching might be important would be the case of one appliance being close to the other and needing to match the stainless.

I looked at both and got the Miele all-fridge column because I liked the lighting and other interior features better. Have had it 2.5 years and been happy so far.

The interior of the Miele suited me better than the SZ, but mine is not an all refrigerator. I don't think you could go wrong with either of these brands.

We had the opposite experience. Looked at the Miele in the store, and couldn't figure out how the interior organization would work for us. But really liked the SubZero. So, that's what we got (BI-36R/O-RH). Couldn't be happier. It is so easy to keep it well-organized.

And it's amazing how well it keeps things fresh. I don't know what the secret sauce is. But food items in our SubZero definitely stay fresh for much longer than in other brands. I was recently travelling for four weeks, and when I came back, items that I had forgotten to remove from the fridge before the trip were still perfectly good. That was quite unexpected.

Having said that, both Miele and SubZero are generally considered excellent brands. If you prefer some of the details on the Miele, you are unlikely to make a mistake if you buy that brand instead.