The H6 has a shade on both sunroofs.
I didn't drive them for long enough to gauge a big difference in them except that the GT is quicker off the line as the max torque is developed lower in the rev range:
GT..........310nm @ 2400rpm I think
H6..........297nm @ 4200rpm I think
Also, the gearing and final drives are the same except the GT has smaller diameter tyres and the GT is lighter by about 90kg (I think) so these conspire to make it quicker off the line as well.
The GT is lower and with the lower profile tyres it obviously handles better, but I really didn't push either of them too hard as the sales rep was sitting in the car with me.
Other than that, when you're moving and you tap down a gear or two they both really get up and fly. These are two seriously quick cars.
From the lights I floored the GT (on a small section of 100km h/way) and in a blink I was at 120kmh. Oh ***** this is quick. I didn't do that to the demonstrator H6 as it only had 30km (I was the first test drive) on the odo so I thought it was too new for that. I treated it softly, but when the sales rep drove it he floored it and it felt as quick as the GT, they both flatten you against the seat. They are both very nice cars. Definitely the best cars I've driven by a long way.
They both sound nice. The GT has a nice low (not noisy) burble while the H6 has a nice induction sound.
I am getting the H6 over the GT for 4 reasons mainly:
1) the H6 has the self levelling rear suspension and in my business I sometimes carry heavy things and this is a good feature.
2) the insurance with a turbo can be expensive
3) I like the refinement of the H6
4) there is more go anywhere appeal with the H6. I mean you can't even go over a gutter with most cars these days
Anyway, there was a good article in the November (I think) issue of Wheels or Motor about the GT Liberty wagon and the 2.5i Liberty sedan. I think they said something about it being one of the best GT's (of any make. Big claim, eh?) ever or something to that effect.
Also, this article link below for youe info.