There are benchmarks... Iĺl look see if I can find you a link. IIRC nforce SATA was faster or atleast used less CPU resources.
GTG look for tha link.
I found this
but it blows away my low cpu utilization theory.
I know it does not awnser your question but it is a reference.
Could you test them by running
hdparm -Tt /dev/sdaX
and post the results here.
BTW does the EPOX board have the 2 mounting holes connecting the CPU cradle to the mainboard?