That's hard to determine, some folks may not like it. But, if it's installed properly and in good shape it should be a plus. If you've already got one, you can buy the top and fasteners to restore it from R&S in London.
A new Webasto folding roof with all needed parts costs about $1,000, not including shipping from England. Of course, that does not include installation. It's made of some space age material, not canvas, so it's very durable. The mohair one costs more, but is rather weird, I think.
If you've got an original one, I'd strongly suggest to restore it carefully and keep it. Again, I think it's one of the coolest mods you can make to a GT6.
Good luck, let us know what you decide!