With the advancement of computer hardware, quad-core prices has dropped down to a level that can compete with dual-core cpu (central processing unit). The quad-core cpu that are commonly known are AMD Phenom X4, Intel Core 2 Quad and the newer Intel Core i7, while dual-core cpuhave AMD Athlon X2, Intel Core 2 Duo and Intel Pentium Dual-core. There are also tri-core cpu that manufactured by AMD call AMD Phenom X3.
When dual-core cpu was released, the hardware advertisers claimed that you can do more things in one time without bogging youe whole system down. That is true, as you can open a anti-virus scanner while surfing the web or playing games while converting movies. Now, software programmers have devised a way to make program multithreaded for dual-core or more, that is, make the program to utilize 2 cores instead of 1. This causes the software to compete for the cores, which also causes the system to bog down.
The arrival of quad-core saves the day, making software that utilizes 2-cores to run smoothly. However, at the same price point, quad-core cpu have lower GHz count compared to their dual-core siblings. Thus, it may seem that quad-core cpu sometimes outmatched by dual-core cpu when using dual-core multithread software. In software that optimizes quad-core cpu, they can beat the dual-core cpu by 50% or more.
Benchmark software such as PCmark or 3Dmark always shows that quad-core cpu obtains higher score than dual-core cpu. Thus we can safely conclude that in the same price point, quad-core should always be your choice.
Power consumption, on the other hand, is in dual-core favor. Those wishing to make a silent home-theater pc are better off with dual-core as they are more silent and less power hungry. Those wishing for performance are wise to choose quad-core cpu to make use of all it's cores.
In the end, if you wish to assemble a computer now, you are better off with quad-core as they are the future. The more is better afterall and you can do more in less time.