Opteron vs. X2?

So, for example which of these would run faster?

AMD Athlon 64 X2 4200+ (socket 939, toledo core) $75

AMD Opteron 175 (socket 939, denmark core) $144

I don't really know much about their opteron processors. So could someone tell me if i should go with the x2 or the opteron? Or maybe explain the big differences so that i can choose myself?

Opterons utilize a different architecture and pipeline design to help streamline HPCs and servers. The pipeline is designed to reduce branch prediction errors and has multiple instruction pools to help solve complicated algorithms without backing up and slowing the pipeline down. In theory the Opteron and similar processors like Xeon and Itanium share similar design philosophies and therefore are faster and more foolproof than mainstream processors. I have never seen it applied to gaming so I don't know what the performance would be like.

Just for comparison, a 3.4 GHz HT Pentium 4 is rated for about 1.8 gigaflops, or 1.8 billion floating point operations per second. A 2.6 GHz Xeon or 3.2 GHz Itanium perform about 3 gigaflops in a single-core configuration. And just to point out that clock speed is only an issue with the size of the pipeline, an IBM PowerPC 4 440 at 700 MHz is rated for 2.8 gigaflops per core (PowerPC 4 is a dual core processor). The Itanium has about 40 stages in its instruction pipeline while I think PowerPC 4 only has about 20. For comparison, a HT P4 has 26 or 32 stages depending on the model, and a Core 2 has only 17 stages per core.