Look around for the benchmarks
The core2duo smokes any other chip architecture on the market at the moment and would be a much better buy than the Pentium D.
Don't be fooled into thinking that the higher GHz on the pentium D automatically make it faster than the C2D because believe me it doesnt.
I can guarantee you everyone here will tell you that C2D is the way to go
edit : see for yourself
http://www23.tomshardware.com/cpu.ht...=433&chart=169