There's a bit of a difference...

We just upgraded our mail server at work from a dual processor Xeon (netburst, aka crap) 2.4GHz with 4GB of RAM to an eight-core Xeon (Core architecture, so about twice as much per core, per clock) 2.4GHz with 16GB of RAM.

It's a bit* faster now.

* - HOLY FUCK IT'S LIKE A BAT OUT OF HELL DOING WARP 9!!!!!!