Go for the Tamron for now, then if you find your missing the reach (can't see it myself as it's only 55mm longer) maybe look at a 70-200 2.8. You can take your pick as to which brand, Tammy, Sigma and of course Nikon if you have the dosh.
Good luck with your purchase and if buying SH ask to see sample shots to make sure you get a good copy.