Bother overclock very similar while the E2160 being faster...however you should be comparing the E2140 and the x2 3600 becuase thats its little brother heh and cheaper.
In an E2140 vs x2 3600 when both are OC'd to 3.0ghz which both can do the E2140 beats it a little bit however it is also 25+ bucks more and the motherboards cost more.