They are as much comparable as a blower to an open-air gpu - because they are blower and open-air AIOs - both keeping the gpu cool. 
In what way is the 240mm considerably larger than the rad card? From what I can tell the rad card takes up 2 slots for the actual GPU (4cm) + a bit more than 2 slots for the radiator (4.5cm? - I'm working of one render here, so I might be off by a bit). The 240mm is using a standard slim radiator (3cm) and standard fans (2.5cm) and the GPU portion seems to be about the same (4cm). So we are looking at a 8.5cm vs 9.5cm thickness. The radcard is longer than an ATX-Mainboard (so about 28cm?) and has a height of at least 11cm, more like 13cm if we calculate in space required for the tubes, which seems to match the rough dimensions of the 240mm hybrid gpu.
While the 240mm is indeed bigger, I would argue the size difference is marginal in comparison to the cooling alternatives. (We where comparing the performance to a blower GPU-cooler with less than half the volume just a few posts ago.)
I agree on the first part. Though would argue the cooling solution is a kludge, and the case design of the alienware aurora should have and could have been easily improved for better airflow in the GPU area. There is for example about 5cm of space between case sidewall and "standard" PCIe height - enough for a corsair one like setup of a slim 240mm rad + slim fans, it would just require extending the vent pattern on the side a bit. Alternatively the bottom of the case is pretty much shaped for airflow ingress with the thick plastic standoffs and "hollow" bottom - just move the HDD trays to the swing arm and you have ample space for a full sized 240 rad with fresh air bottom intake. Of course that's on Dell/Alienware and Asetek had to do the best designing around those "constraints".
What I don't see is how this design can be applied in a situation other than a combination of ample space and horrible airflow while still maintaining an advantage over alternatives (Open Air Coolers with a hypothetical 4+ slot width - think Raijintek Morpheus x2, "standard" Hybrid GPUs, or just good open air coolers with a lot of extra space for air to move around).
I believe it has been established that blower are generally inferior to open-air designs when it comes to GPU cooling in good airflow conditions. It would surprise if that wouldn't hold true for Hybrid-AIOs. There are no inherent space savings associated with a blower radiator as opposed to an open-air one. One could easily manufacture a "frame" you could screw a standard radiator to, that slots into a PCIe slot, but having the air-ingress directly flush with the outside wall for large volume fresh air intake (or air-egress for directly dumping the heat outside) is obviously superior.
