Both seem to have more or less the same specs but personally, i'll lean more towards the Abit simply because it carries an onboard 7 series nvidia graphics chipset with DVI output as opposed to the Asus's 6 series graphics with only d-sub.
You cant go wrong either with the x2 3600 or the 3800 as they are both excellent cpu's. If you want to invest in a aftermarket hsf, then the oem x2 3600 is your better choice as it doesnt come with a hsf. Plus the 65w runs cooler and takes less power allowing a higher overclock...so...yea.