Hey! So I have a d750 and have been itching to get a real long telephoto lens. I have and love the nikkor 80-200 2.8, and am now wondering if I should pick up last year's Tamron 150 - 600 5-6.3 or wait a few months and grab a new sigma contemporary of the same specs. I've really become a fan of sigma with their new lenses, but the tamron has got great reviews and is nearly identical price and spec wise. What to do?