Full rafter insulation roof or insulation on concrete slab

https://www.hausbau-forum.de/threads/dach-Dämmung-auf-geschossdecke-oder-unter-dem-dach.36573/

we are planning the ceiling on the upper floor as a concrete ceiling instead of a wooden construction - now it’s about the insulation in the upper floor/roof. [...] The roof apex is not used as living space by us (town villa - 2 full stories), but only as utility space.

Since full rafter insulation is of course significantly more expensive, the question arises here whether the insulation on the concrete ceiling is sufficient?

Oh, if only the OP would just get into the habit of linking their main threads about house planning when asking individual questions. I currently don’t have time to dig deep into your thread history – so I can’t really assess what sense it would make here to put a concrete ceiling on the upper floor if there’s only storage space above. Hardly anyone would store coal there, would they?

Yes, I fully agree with the idea of a ceiling instead of a roof here – considering the consequence of a cold-blooded storage room – but I just can’t follow the question of why concrete.