Having had the 7-seater for a while now I can see the appeal of the 6-seater if you're using the 3rd row a lot and don't need the extra cargo space or seating position. Especially in Dog carrying if you have a dog who can chill out on the floor (some can't). The extra foot room under the captains' chairs and the lack of a center headrest would be nice once in a while. Then again, it's also nice to have the dog contained somewhat in case of emergency.
Also, re: cargo space behind the 3rd row in X - it's fine, it's just vertical instead of horizontal because you need to use the trunk well and then stack anything else above the load floor. Same as our neighbor's odyssey gets used IRL (they just ditched the rear floor and let the well underneath swallow backpacks and such in a pile). And, of course, frunk. My favorite feature of the car is how much room for people and crap they packaged into a vehicle that's significantly more compact than a minivan, considering it's also equipped with two variable-geometry hardtop convertible tops and shaped like a suppository with a handle on the back. The 6-seater blows some of that up but it's not like anybody really needs an 8'x4' sheet of drywall that often