Gigabyte has a stronger reputation so I would go generally go with them over Palit. Some of the latters heatsink/fan arrangements have not been up to par with other brands.
Have you checked for reviews for the specific cards to see if either has any issues? Since some manufacturers have multiple versions of a single moded, it is best to find the exact card if possible. A good site to find lists of reviews by model numbers is:
http://www.gpureview.com/search.php
Here is a THG roundup of multiple cards, including a Gigabyte and Palit card - be careful to note feature differences and how they relate to cards you are looking at, for instance the Palit in this review is overclocked. Note that despite my comment above the Palit comes off pretty well in this review.
http://www.tomshardware.com/reviews/geforce-gtx-460-roundup-gf104,2714.html
Why are you limiting yourself to Palit or Gigabyte? Generally I prefer EVGA followed by XFX - many of the latters cards include a double lifetime warranty. My favorite used to be BFG, but I guess they made their cards so well, and backed up the warranties, so they did not make enough of a profit.
I suggest taking a look at the following website for more general information about brands and suppliers:
http://www.upgradevideocards.com/brands.html