The steam oven will only cook by introducing steaming. A combi will do the same steaming, but can also use dry heat, like a convection oven, and can also use both steam and regular heat together, which cooks foods more quickly than just dry heat.

Are there steam ovens that are also microwaves? Or only steam-convection combi?

I think Sharp made a steam combi with microwave, but not sure if they still make it. There are plenty of microwave - convection ovens. There are also steam only, and steam convection ovens - which are referred to here as combi's.

(Cross-posted in other Miele Steam Oven threads)

We bought a Miele DGC 6800 Combination Steam Oven (non-plumbed) and a few months later on a whim descaled the unit. Right after the descaling process, my Miele steam oven gives me a 'Fault 20' whenever I try to do steam cooking. The regular convection cooking works fine. Wish I had something else!

It's out of warranty even though we probably used it about 20 times. Now Miele is asking for $150 for a technician to come out and pay an additional $90/hr for labor + $ for parts!

If you cross-post, can you please also post a link to the one location that you want the discussion to happen at. It's not very helpful to spread this out over half a dozen tangentially related threads.

I suggest linking to here: https://www.houzz.com/discussions/5851297/fault-20-on-miele-combination-steam-oven-dgc-6800-xl-cross-posted

Yes, you get all of the features of a steam oven and more. If you buy a combi-steam oven there is no reason to buy a steam oven as well unless you want to steam more food at one time than you can fit into the combi-steam.