The claim that it vents as well as an island hood only makes sense if the island hood is undersized and too high. There's no way it can vent as well as an overhead hood against a wall. OTOH, claims aside, the 18" rise is better than flat in the counter. The issue is that the plume of that which is being sucked has to bend across the stove to get to the extractor. There's a real issue, however, if it's strong enough to pull the plume, it may also be pulling on your flames.

There are hoods that look nice in front of windows, and others which are much wider but thin and sit higher up, or even in the ceiling.

A lot of this depends on your personal tolerance for looks over function. I'd go with the hood in the window, or even better, placing the range on the wall between the windows.

To supplement pillog's comment, consider the following.

In the image above, a commercial hood with a tad too little air flow is attempting to capture and contain rising hot air from a hot cooking surface. Because this is a commercial hood, the gap between the cooking surface and the hood is probably four feet. The heat-induced variations in the index of refraction of the rising hot air are imaged by schlieren photography.

Now imagine an 18-inch pop-up at the back (left) of the cooking surface. It would dimensionally be a bit more than a third of the height to the hood. It would have to move the rising hot plume from near the front of the cooking surface to the back and into whatever aperture was provided on the pop-up. Considering that the hot surface can generate a greasy plume rising at more than three feet per second, to get the plume to deviate steeper than 45-degrees to vertical would require a horizontal air velocity around 3 ft/min at the front, corresponding to some large multiple of that at the pop-up where the narrow dimension is (guessing from the pictures) not over 4 inches or one fifth the distance to the front of the range-top. The pop-up air collection aperture might be a tad loud under those conditions if enough air flow could be achieved.

And on the subject of airflow, it looks to me from skimming their literature that Best failed to mention that the rated flow rate of their blowers is achieved hanging in the air, and not sucking air through a narrow width pop-up and thence via a duct (that may have an elbow behind the range and one below). For the higher flow rates, one would use an 8- or 10-inch duct; but that would require significant spacing from the wall to even hope for a configuration like Best shows in the their brochure. Perhaps an 8 or 10-inch duct could go straight out the wall to an external blower. My sense is that getting much more than 300 CFM through a 36-inch by 2-inch pop-up (0.5 square foot) would be a challenge for the listed blowers, perhaps even with their largest blower, but this is dependent on many factors. (300 CFM flow is 600 CFM/sq. ft. in the pop-up, maybe 300 CFM/sq. ft. at the pop-up aperture. For comparison, I pull about 90 CFM/sq. ft. through my Wolf Pro Island hood aperture. But being a hood, it makes use of the rising plume velocity to aid capture; the air flow is mainly to aid containment when the hood is large enough.)

So, bottom line, ignoring flame disturbances if applicable, the Cattura may be able to capture hot greasy plumes at the rear burners, but I would doubt that it is effective at the front burners except for what Best showed in their video -- steam -- which has a low upward velocity above a pot compared with hot grease plumes from griddles, woks, and grills.

In any case, I would suggest taking any opportunity you might have to witness a demonstration of effectiveness and noise. A demonstration is worth a 1000 analyses, including my analyses. For a demonstration bring a pan and some peanut oil and heat it to the smoke point. Then you can see the results without schlieren photography, and you can decide on the acceptability of the noise and the potential for escaped grease and odor. One does have some control of where particular foods are cooked relative to the pop-up.

Downdraft is a poor performer no matter how much power you strap to the blower. I think that's been pretty well covered. With overhead hoods, even there 'capture area' comes into play, where a nice cavernous hood is more effective than a sleek modern design. If you're looking to balance functionality and form, you can always go wider on a low profile hood, maybe a 48" for the 36" range. Here's an example of a hood in front of windows that manages a great clean look. https://www.houzz.com/photos/saskatchewan-lakeside-retreat-transitional-kitchen-phvw-vp~2221872