I rarely fear what a marketer of just about anything tells me. I fear the information they conveniently leave out!
The main advantage with a direct Peltier vs. a compressed system is that the compressed systems as I've seen them all come in very cramped cases and trying to add water cooling for even one video card is very hard and for two?... I guess anything's possible, but for all the compressor noise and space limitations, for what little you gain over a properly done Peltier system, I'll stick with the Peltier! Going from -5 C to -35 C you gain.... 2%!!! Yeppers, as impossible as that may sound, that's all you get! Problem is the doing the Peltier right which is rarely done. almost without exception it takes a very large Peltier attatched to an efficeient water block and run on its own power suppy. It must also have very, very big external radiators to rid yourself of all that heat. After all, the Peltier runs at a factor not exceeding like > 69 F of what the water temperature is. Let the water heat to 45 F and you'll suffer as well on a Peltier system.
In fact, it may be unpoplular to point out that properly done water cooling alone takes you most of the way there as far as cooling goes. I got all the way from 3.2 to 4.0 on water alone, but it was water with the more efficient water blocks and big, external radiators. Half measures will yield 1/4 results as far as I've seen.