The processor world used to be only Intel, now there is another contender, AMD (Advanced Micro Devices). A couple years ago when AMD first made its way into the scene there were many incompatibility problems with AMD processors and programs. However due to changes in the design these incompatibility problems no longer plague the AMD line of processors. But it is a known fact that an AMD equivalent of any Intel processor is about 30 to 50 MHz slower than the Intel counterpart. Up until recently AMD has had a boost in speed, that Intel has lacked, in certain games due to 3DNOW!, a SIMD (Single Instruction Multiple Data) technology. But with Intel's new line of processors named Pentium III they now have their own SIMD, KNI (Katmai New Instruction). AMD's line of processors used to be able to keep up with Intel using 3DNOW but with KNI Intel will once again take a very large lead in speed.
Thus I believe Intel builds better and faster processors than AMD.
The first ever problems AMD had were with incompatibility problems that plagued their entire line of CPU's until the K6. These problems hurt AMD because nobody wanted a CPU that could not run 15% of the programs out. People wanted a processor that had programs optimized specifically for it, people wanted a computer with a sticker that said "Intel Inside" because they knew every program would run on it. If people wanted a cheap solution then they went with the low-cost AMD CPU and faced incompatibility problems with a lot of programs. But most people were willing to spend the money to get the genuine Intel processor and this is a major reason AMD became the underdog and left Intel to reign as King.