So I was off by 0.5cm - the Kingpin is 19% bigger than the Rad-Card instead of 12%. They are very much comparable size-wise.
The Rad-Card is 100% bigger than a standard 2-slot blower or open air GPU. Those are very much NOT comparable size-wise.
A setup with the Kingpin radiator drawing air from inside the case and exhausting it to the outside via a bottom- or side-vent has exactly the same constrains regarding recirculation and fresh air intake as the Rad-Card. AIOs in general should never have issues with air recirculation, so that's not something you can differentiate both solutions on. The minimum spacing requirements seem to be the same, though the blower style would suffer less from tighter spacing due to higher static pressure. But even a blower can't magically generate fresh air inside the case and needs to draw it from somewhere, requiring a gap on the intake-side.
Such a setup could have been possible size- and geometry-wise in the very case the Rad-Card solution was designed for - but wasn't due to silly case design decisions. Which is (again, just to reiterate) not an issue with the cooling solution but the horrible case design.
One could argue (this would have to be tested) that drawing fresh air from the outside through the main radiator and exhausting it via the blower portion is an even more efficient orientation (especially considering the cooling requirements and thermal tolerances of the vrm) of the Kingpin solution, creating a full air cycle. An option that's not possible with the Rad-Card.
As far as I can tell a standard blower design excels in a very narrow subset of situations where there is no space whatsoever for airflow, radiators or extra fans to move heated air, that require the card to run an inefficient double duty of both cooling the GPU and removing the heated air from the case over a long, narrow airpath.
With the size of the Rad-Card this constraint obviously can't be the case anymore. There has to be at least enough free space in the case for another 2 slot PCIe card (realistically more due to fixed PCIe spacing and intake air gap requirements). Space that could be used for radiators, intake/exhaust fans or airflow.
You can't argue that the Rad-Card is awesome because a blower works in a specific situation and then disregard that the blower to a big part works well in those specific situations because there is not enough space to fit anything else, including a bigger Rad-Card.
I would like to see those "media center styled PCs" that have enough space to fit a Rad-Card like setup, but no kingpin or even 3-slot open-air + exhaust slots/fans setup or at least couldn't be made to fit those with minimal design improvements.
I'm genuinely curious what you believe those unique situations are, where this can be the superior cooling solution. The Aurora (at least to me) clearly isn't it. It's just a badly designed case that is saved by a well-engineered kludge.
