Air-water heat pump: split or combined unit?

We can choose between a Viessmann split unit (plus ventilation) and a Stiebel Eltron combined system (including ventilation) through our house provider. Both are air-to-water heat pumps.

What I find on the topic are mainly considerations about space or noise, which is understandable. However, I am also interested in the question of how efficient these devices operate. I only find general statements that there are hardly any differences between split and combined systems, but from a thermodynamics perspective, this makes no sense to me: Split units have intakes outside the house with diameters of 60-80 cm to be able to draw in enough air. The more air you draw in, the less energy must be extracted from each unit of air, which increases efficiency. A combined unit, on the other hand, has only a 30 cm pipe to the outside, which massively reduces the volume flow, so the air must be cooled much more to obtain the same amount of energy. Therefore, in my opinion, it can never run as efficiently as a split unit. But I find zero statements on this, nobody seems to be bothered by it, and I can't be the first to think about it. Do I have a flaw in my reasoning, or do you have other insights on the topic?

Thanks in advance! If you have other aspects regarding the comparison of the two types, I am also very interested.

We had the Tecalor THZ 504 in the old house (which is basically identical to the one from Stiebel Eltron), it is a combination unit. In the new house, we have a split unit from Viessmann. In terms of noise, I still notice few differences. In the old house, the Tecalor caused the noises, in the new house it is the separate ventilation system. The noise level is comparable. We were satisfied with the Tecalor. I found it surprisingly affordable, in the second year we spent about 50-55€ per month for heating, ventilation, and hot water preparation. It was probably a mild heating period, but that was already inexpensive. We haven’t lived in the new house long enough yet for me to present you with reasonable comparison data. The first winter is still ahead, the second even more so. Currently, the electricity consumption seems significantly higher to me than in the old house. But it is also a bigger house, and still damp since it was only recently occupied. Unfortunately, I cannot say anything about the technical differences / comparisons of pipe size, as I lack the expertise.