I dont have a Miele, but I do have a Thermador steam oven. Although we have another oven, and to be honest, i wasnt sure how to use or if I even would use a steam oven, It turned into my go to oven for so many things. I use it for almost every meal because it does a bit of everything easily. Thermadors oven is a larger, once you use it and get to know how useful and versatile they are, you will find yourself using it more and more. I would get the larger oven.

I got an XL. I don’t think the extra space would benefit me. I also have a Miele speed oven and convection oven, so like you, three ovens. i suppose you should consider whether the functions that you can get only from the steam aspect are the most important to you. If not, I would think the XXL would be unnecessary.