G350 BT or G500??

Moin together! It has been dealt with from time to time, but not really in detail, so I dare to ask the Gretchen question again: G350 Bluetec or G500?? I drive in the year 30,000km plus X, the fuel costs are quite important to me, but not so important to me that they would basically exclude the 500er. I would like to keep the new G in the long run, let’s say the next 10 years. So also the topics durability and repair vulnerability are for me Very important. Rightful smooth running, durability and permeability of the 500s? Please also give me an info if you have own experience values regarding consumption and repairs at the 350s and/or 500s. One will definitely, the question is: Which one? Therefore my question to you: Which would you choose and why?