64 bit - Should I setup x86_64 system on Atom 230?

I've got mini-ITX motherboard (945GCLF, afair) and I always setup only 32-bit OS on it.

But few weeks ago my father told me that I should use 64-bit OS for this processor.

What can I get from changing architecture? Will it speed up something?

In general, does it matter which architecture I use?

P.S. I've got 2 GB RAM and use Archlinux.