The Tammy is around $400 and the Nikon about $1000.
Please post pics to support your opinion.
I think I need one of them.
I have not even touched either of these lenses, but, the question whether any lens is twice as better because it's twice the cost is spurious.
Many photographers will be happy to pay twice the cost of a Nikon over a 3rd party to get just a 5% improvement