I can't speak for the double but the City Mini GT turned out to be very disappointing. The basket is hard to access, I have a hard time getting stuff in and out. I took it on the beach and sand got in the gears so now it makes an awful clicking noises and veers right. The company has been helpful in getting the wheels replaced but when they said that the brake assembly needs to be replaced, it sounded like more trouble than its worth because I want to replace it for a more narrow and lighter stroller anyways.
I am shocked to hear you say this as I totally LOVE mine! Do you have the latest model year? I have no issues with the basket. The rear bar is curved for easy access, the sides are stretchy so it is easy to access from the rear or sides, and it is pretty big. The handbrake is awesome, the sunshade huge, and overall it is fabulous. It is not designed to be used on the beach, so you really can't fault it for that. Pretty much all strollers would struggle in sand. Anyway, I think it is a fabulous stroller. No comment on the city mini double, but I know most moms love it. Baby Jogger is a great company, so I say go for it!