I tried both and walked out the store with the tamron mate..its a cracking lens!
The vc is amazing and its very well built.Bit larger than the nikon but I preferred its size.Image quality is very good and rivals maybe tops the nikon at certain focal lengths.Heres a link to a thread with some sample images.
http://www.nikoncafe.com/vforums/showthread.php?t=289253