The more powerful the processor, the faster the system goes. Clock speed alone, however, may not be the determining factor. A 66 MHz Pentium system, for example, is faster than a 66 MHz '486 system, because the Pentium chip is inherently more powerful than the 486. On the other hand, a really fast '486 may still beat a slower Pentium. Memory is almost as important as the processor you choose.
Memory is the temporary workspace that the processor uses to store and manipulate information.
Any programs that you use must be loaded into memory, along with the information they use, such as text documents, pictures, sounds, etc. If you skimp on memory, your processor can't work up to its full potential. You may actually get better performance with a less-powerful processor and more memory, than you would with the most powerful processor and less memory. Hard drive space is somewhat less critical. The hard drive is where you store your programs and information.