co-hole basically covered it.  The only thing i'd add is that AMD puts most of their research and development into making their chips really fast, while pentium tries to make them reliable.  Athlon is faster, but it runs hot, so make sure you have a thermally advanced case if you get it.
Life is not a journey to the grave with the intention of
arriving safely in a pretty and well preserved body, but rather to skid in broadside, thoroughly used up, totally worn out, and loudly
proclaiming...'Wow! What a ride!'