Base slab vs strip foundation

Hello.

The strip foundation is supposed to be cheaper, according to the architect. We are planning a single-family house with a basement.

In my opinion, however, such a foundation would actually involve much more work, whereas the slab without a strip foundation would simply get a few centimeters more concrete... Labor hours often cost more than just material.
We don't have any offers yet, as we are not that far along, but I would still be interested in your experiences.

The energy consultant prefers the slab, as it is easier to insulate, with less risk of thermal bridges - which makes sense to me at least.

What are your experiences with this topic?

Thanks and regards from [Schwabenland].

I and also our expert prefer a slab, even without insulation. However, depending on the thickness, a few thousand worth of concrete can go on there... What does the structure without a slab actually look like?

What does the structure without a slab actually look like?

I can't say yet, as the architect has so far planned with a strip foundation. The new idea towards a slab came from the energy consultant. He said a plain slab would probably be 5 cm thicker than one with a strip foundation. We still need to discuss with the architect exactly what would change in the structure. I wanted to first gather your experiences.

What should change in the structure besides the thickness of the slab?

Do I just have a knot in my head? You always need a slab foundation - and a basement doesn't need a strip foundation, but rather just a slab foundation?

Unless it is located on a slope...

Do I have a knot in my head right now? You always need a slab foundation - and a basement doesn’t need a strip foundation, but just a slab foundation, right?

Unless it’s on a slope...

What does that have to do with the slope?

Because you then cannot found frost-free with just a floor slab...