Warm weather area here, but I vastly prefer the hard top. The spider looks incomplete to me.
I've never personally liked convertibles, so my vote is GTS/GTB. With that said, however, I think the 355 Spider is the best looking convertible ever made as it looks like it was made to be a convertible rather than appearing to be an afterthought. For me, one of the most attractive parts of the 355 is the curved glass rear window which is another reason I prefer GTS/GTB.