All of these seem really nice, and they have similar features and build quality. In the end, we decided on SZ for the simple reason that they have the longest track record and have demonstrated that you can get spare parts even decades later. A lot of the other brands haven't been in this market for that long (at least not in the US). So, it's always possible that they'll pull out again or that they'll drastically change their product design making it difficult to do repairs when the fridge fails 20 years down the line.

A big benefit of high-end brands such as SZ is that a) they tend to be built more sturdily than cheap mass market products from the big box store, but more importantly that b) they are built with repairability in mind.

We had a 36" SZ fridge / freezer combo in our last house with an inside water dispenser. No external ice dispenser. I have mixed thoughts on it. It was all we could fit in our kitchen and to make up additional fridge space, we installed two fridge drawers in our island to hold our produce. I found that the fridge was too small to hold all of our groceries. We are a family of 4 and eat a lot of fresh produce. The other thing I did not like about it was that the ice maker was in the freezer and the tray took up almost an entire drawer of freezer space, thus making the actual useable freezer space extremely small. We kept an olde side-by-side in our basement to store additional frozen items (homemade soups, tomato sauce, etc).

All that being said, our food was always fresh, nothing ever rotted or broke down prematurely. Nothing ever had freezer burn. We ended up moving out of that house one year after our kitchen remodel was complete (husband was transferred). We are redoing our kitchen now and installing a 36" SZ fridge column and 36" SZ freezer column because I really do love their appliances.

I have no experience with Bertazzoni, Thermador, or Bluestar refrigeration. TBH, I didn't even know that Bertazzoni and Bluestar ventured into that market.