I would choose Convertible. I just love these amazing sport cars, and TT is one of my favorite cars. I do like the Q7 but I like TT more, and I would more like a car like TT/Audi R8 than a big car like Q7.
But if I had kids, then I would go for the Q7 and maybe have another car, but just a cheap one. The TT isn't that good if you have kids, because you cant drive all in it.