I always close the blind when parking in this heat and then leave the blind closed but open the roof when travelling. Anything above 40 mph and there's too much noise anyway. I also get nervous about visits from seagulls (leather seats would have been better!).
How hot does it be one where you are? We are in the middle of a mini heatwave in the Uk at the moment, 27-31c in London. The air con seems to cool the car down quickly and I always park with the blind closed to reduce the heat build up.
On balance for me the sun roof is a definite plus currently but I don't know how it would be if I was driving in 35 or even 40 degrees.
Glass roof a must for me , and lets not get carried away with our last few days of very nice sunshine , it won't last to long but my sunroof will . It's the light you get from it all year long . Expensive but brilliant extra