It's not clear what you're asking. Are you considering buying both the 1066 and the 800 RAM and installing them both?
Or asking which to get or which can you run?
sorry bout that - im asking because I have just bought 2x2G of DDR2 1066 and already have 2x2G DDR2 800. I was wondering if its possible to run 1066 with 800 on the same motherboard - and have both run at full capacity