There IS one other major aesthetic difference that hasn't been pointed out at all in this discussion. The metal roof is body-colored, including the A and C pillars, while the glass roof has the two-toned shiny platinum colored framing and pillars. If you're NOT a fan of the two-tone look of the Air Touring and Grand Touring, then choosing the metal roof makes a huge difference in the exterior look of the car.
Metal roof with non-stealth is the cleanest look for the exterior body, in my opinion:
View attachment 15938
If you choose glass canopy (non-stealth) then you now have the two-tone look... and for me personally, i just don't care for that look (at least with the darker paint colors):
View attachment 15939
So, you might then choose "stealth" to get rid of the bright body work... but if you choose the glass roof with stealth, you now get blacked-out pillars and upper sections, so it's still two-tone, just different two-tones:
View attachment 15940
I'd like that stealth look if the top section could be body-colored rather than black... but that's not an option with glass roof. With glass roof, your top half of the car will be either platinum colored (non-stealth), or black (stealth).
You CAN choose stealth with metal roof... and then top-half is indeed back to body-colored, but the other small platinum bits blacked out... which is s nice look:
View attachment 15941
In the end, for me, I really like the exterior look of the metal roof in the body color, since my car is likely to be red. I just don't like the two-tone looks that you get with the glass roof, whether or not you choose stealth or platinum look. Less of an issue with a black or silver car I guess, but a bigger issue on the red car.