From performance point of view the Pentium is clearly superior, but from power consumption perspective, the Atom is the winner. It's always about consumption vs performance trade off. Depends on how you define "better".
Will there be much difference in gaming? The D525 is coupled with ION 2 and 2GB RAM whilst the Pentium has an ATI 5470 and 4GB RAM. I know neither are going to be any good, I'm thinking games like COD2 and SIMS 3, San Andreas...
Based on the given specs, the Pentium is clearly superior. Just don't expect too much out of it. :P