ESX servers and Memory Types

I want to use 2 IBM servers as esxi hosts in a cluster:

CPU - 2 x 2.53 Ghz Quad-core Xeon - E5630 it supports 1066 MHz RDIMMS

CPU – 2 x 2.60 Ghz Xeon 8-Core Xeon E5 it supports 1600 MHz 1600 RDIMMS

Will the different clock speed affect performence?

Whats the maximum memory recommandations for each server?