Revan,
The 540's airflow is definitely easier to see. But Atminside's empirical testing showed the GPU was well ventilated in the PC-o8, even though it's hard to see how that works. And I have to think Lian Li had good reasons for the design, I just wish they'd explain them.
I'm still using the old Fortress FT02, which despite it's age is still one of the best airflow cases ever made. 3x180mm fans at the bottom blowing straight up over a 90 degree rotated MB so the graphics card is at the top of the case, with air from a 180mm on each side of it. It's a great case, though so heavy I had to make a wheeled cart for it to be able to move it around, but it completely lacks good radiator mounting sites, and I'm starting to get into water cooling just as a hobby, not really because of any benefits it gives.
What I really like about the PC-o8 is the idea of mounting a 3x120mm radiator behind those 3 fans on the PSU/HDD side, so it's getting some of the benefits of an intake--fresh cool air from outside the case--without the usual downside of intake--blowing hot air over the MB. But I'm just going to have to understand how the MB side is getting cooled before I can pull the trigger on it. Lacking that, I'm looking at the 540 too.
Money isn't really an issue at this point in my career or I wouldn't even be considering the PC-o8. If you're building with a budget, you'd definitely be better off with a cheaper case to free up money for more important hardware. For me, it's not really about pragmatic value at this point, its about blowing cash on a hobby I enjoy to reach an excessive ideal of water cooling that looks how I want it to look, but that in the end won't really even help the system's OC potential or longevity over a much cheaper case with air cooling. It's like looking at a Cadillac when you known a Camry is better on every practical measure.