The Dacor downdrafts are probably among the best. They rise 10-15 inches above the surface. However I have pans taller than 15 inches. How effective would the downdraft be at venting the steam from a pot of pasta when the steam emits above the vent? It won’t do anything more than the bathroom fan. Flame up some alcohol in the pan - nothing. Blow torch a sous vide chuck roast - nothing. Manage to burn some flour in the pan so it smokes up - nothing. They do technically vent the room but they are ineffective as a “hood” for containing smoke/smell, grease, etc.
Do people really run those hoods when they boil pasta?? I don’t. After all, the steam humidifies the dry winter air.
Pan-frying things is a different issue. Messy stuff? There is the grill for that.
I run my hood all the time. In fact, that’s the first thing I do when cooking. In my hood, the low setting is so quiet, I don’t mind leaving it on. With the fan on, the house is spared from cooking odor.
I would need more than two burners. I have 5 burners. don’t use them all simulteneously but they do different cooking, a tiny burner for a small sauce pan, two medium sized, one big one that boils a cup of water in a minute that I use all the time and a jumbo for a wide frying pan.
I also have a leaky house and didn’t have problem with a high CPM vent.
If I remember correctly, the American oven range gets hot and heats the floor underneath. I liked their gas range because of the open burners.
A lot of this has to do with climate. People who live where it gets cold and there is 2 ft of snow on the ground are not as likely to just pop outside to use a grill! If your house is closed up from at least October to April because the heat is on you NEED a good ventilation system if you are an active cook or your entire house will stink of spices and smoke.
I’ve been known to grill in the snow. 
But I still need a good fan. It’s actually kind of frightening how much grease ends up in it.
"How effective would the downdraft be at venting the steam from a pot of pasta when the steam emits
above the vent? "
Mine vents the steam just fine from my tall pots.
Agreed that the strength of down draft fans is less than that of industrial strength over head fans, but having a hulking overhead hood would not work in my kitchen.
My cooktop is not up against a wall, but is in an island.
I’ve always liked the curved glass hoods for islands. http://2qaayg3yvidcn9imquz625sg.wpengine.netdna-cdn.com/wp-content/uploads/2016/09/island-vent-hood.jpg
Gorgeous, unique, fabulous granite made by nature vs. man-made resin? No contest for me. Even as it goes out of style, LOL. If we ever do update here, it would be with selling in mind at that point so I’d go with whatever is recommended at that time. I like concrete compositions I have seen, they can be very nice and certainly unique. I also love soapstone but it would just be too dark for our kitchen.