Memory question...

hi guys i need your advice...

i have an Athlon XP 2400+ FSB 266 and two memory modules 512MB PC3200...
the motherboard supports 400 Mhz DDR and Dual Channel (Nforce2 Chipset)...

which of the following options is the best... (without any OC)

run the memory at 400 Mhz with 2.5/3/3/6 timings or...

run the memory at 266 Mhz (in Sync with the FSB) with 2/2/2/5 timings...

Note: the memory timings are detected by SPD

thanks...