NEED HELP!!! HyperX PC3500 CA2 or HyperX PC3700 CAS3???

NEED HELP!!! HyperX PC3500 CAS2 or HyperX PC3700 CAS3???

Hey guys I placed an order for a Kingston HyperX PC3700 512 stick 5 minutes ago but now I am doubting it because it's rated at CAS3 and the timings are slower than the HyperX PC3500 which is rated at CAS2. WHAT SHOULD I DO??? Go with higher clock speed and looser timings or tighter timings and less clock speed?

I have 20 minutes at most to change the order.

THANKS FOR THE INSIGHT!!

The exact specs for the PC3500 are : 2-4-4-8-1T (CAS Latency 2)
The exact specs for the PC3700 are : 3-4-4-8-1 (CAS Latency 3)

Edit: It will be used on AMD XP2800 on Abit NF7-S board

I would go with the Hyper-X PC3500 for an AMD system. The tighter timings will be more beneficial. For a P4 rig I would go with the Hyper-X PC3700 as the tighter timings do not seem to matter as much.