This Gigabyte 660 is only slightly more expensive ($15, $4 shipping but $20 instead of $30 rebate):
http://www.newegg.com/Product/Product.aspx?Item=N82E16814125443
Gigabyte board advantages:
- slightly faster (betwen 2.7% and 8%; average maybe 5%; see GPU BOOST comment at bottom)
- quieter (*quote from video, "the cooling was incredibly efficient")
- more reviews (all good)
- probably higher quality
- Gigabyte has GREAT support in my experience, but I've heard complaints from people about Galaxy.
Cons:
Slightly more expensive (unless the Rebate doesn't work).
GPU BOOST:
The new Kepler (GTX600 series) uses something called "GPU BOOST"; it's similar to Turbo Boost and allows the cards to overclock, if needed, by a small amount.
I'm stating this because the Gigabyte card linked has better cooling so it's going to be faster than the Galaxy in situations that it requires this (any time you can't achieve the highest set frame rate such as 60FPS). This is in ADDITION TO the already higher base clock.
So basically the Base Clock for this board is 2.7% higher than the Galaxy but in some cases this Gigabyte will boost whereas the Galaxy might not due to the temperature. That difference can add up to 8% maximum.