Good memory for new Core 2 Duo

[Windfire]

I'm trying to understand which of the following I would want:

I'm looking at the following Corsair options:
http://www.corsairmemory.com/corsair/xms2.html#twinxms2

The two I'm focusing on are:

Corsair XMS2 2GB 240 pin DDR2 800 Dual Channel TWIN2X2048-6400C4
Latency 4-4-4-12

Corsair XMS2 2GB 240 pin DDR2 1066 Dual Channel TWIN2X2048-8500C5
Latency 5-5-5-15

The motherboards I'm looking at support both 800 and 1066. What is preferred?

Thanks,
Steve