Evening mate!
Mine is a MkV but I went with the cloth on the basis that it felt a bit more authentic as a GTI and it held you in your seat a bit better when giving it a bit of stick. But that comes down to personal taste.
With regard to caring for the leather, I know that the leather in the MkV tended to wear quite easily, especially on the seat bolsters. Indeed, this seems to be a common problem for a lot of VAG cars, the mkII TT really suffers with it.
Not sure what the MkVI guys have found so far, but then they may not have had theirs long enough to get any issues with the leather as yet.