Hi GregoryH.

I'm very new to this site. However your thread is very interesting (I've go the same problem). I have no numbers or previous experience with either of these lenses but I have jumped between a lot of review sites. I agree with arthurking83 except for the first two places.

1. Sigma (then)
2. Tokina
3. Tamron
4. Nikon (because of the price)

Sigma only for the extra mm. At the end of the day you can worry over it to the point you cannot make a decision and miss out on taking great photos. Every lens will have a problem, it just depends if that problem will significantly interfere with what you will primarily capture.

Let us know what you eventually go for and how your trip went. Good luck.