Well, Speed wise you lose about .6GHz.
You can't just multiply the speed of a Core 2 Duo by two and then compare it to a Pentium 4. The Core 2 Duo and Pentium 4 are each based on entirely different microarchitectures. The Core microarchitecture is much more efficient at handling instructions than the Netburst microarchitecture (which is what the Pentium 4 is based upon). Therefore, any Core 2 Duo will best any Pentium 4 in anything you do.
To give an analogy...
Imagine the 3.0ghz Pentium 4 as a paperboy making his routes. He can ride down the street at 30mph, but he's rather clumsy and only manages to throw out one paper by the time he reaches the end of the street. He must then turn around at go back down the street to deliver the rest of the papers, one paper at a time. Now, the 1.8ghz Core 2 Duo is also a paperboy. He goes down the street at only 18mph, but has much better coordination and manages to throw 10 papers by the time he reaches the end of the street. Not only this, but on some special streets (multi-threaded applications), his friend helps him out by also traveling at 18mph while managing to throw 10 papers. Who do you think will get done with their route sooner?
Edited by stettybet0, 06 August 2008 - 09:19 PM.