A CPU doesn't just boil down to the number of cores it has; performance, or the lack thereof, depends upon the quality of its architecture, design, and implementation.
Things you need to consider:
{*} Core count (you've already got this)
{*} Threads per core (how many concurrent threads can run on a single core? For example, Hyperthreading on Intel's CPUs splits one physical core into two logical cores; in other words, each physical core can process 2 concurrent threads)
{*} Cache (L1, L2, L3, L4): the amount of cache is important, and cache coherency is another issue (I won't get into this because it might be above your level of understanding). Right now, the important areas of focus are L1 through L3.
{*} Memory-controllers, transistor count, clocks per tick, etc...: Not going to touch this.
So, which is better? Between 1999 and 2006, AMD's processors literally thrashed the best Intel could muster (minus the P3s). However, Intel was able to get back into the game in 2006 with its Centrino-based line (i.e., the Pentium M and Core Duo), which heavily borrowed from their Pentium 3 architecture. The Pentium 4 architecture was horrible and was ultimately abandoned in favor of the older Pentium 3 architecture. Interestingly enough, the processors by Intel were so good that people literally took the Centrinos from laptops, used a base converter, and used that processor instead of the crappy Pentium 4 (e.g., a 1.8 GHz Centrino laptop processor outperforming a 3.2 GHz Pentium 4 Extreme edition). When Intel caught wind of this, they began to pay attention and ultimately the same Centrino technology would find its way onto the desktop scene.