Intel and AMD are competing processor manufacturers and have a few subtle differences in how their processors operate.
One difference is that AMD chips do more work per clock cycle than Intel chips. A 2.2GHz AMD is comparable to a 3.0-3.8 Intel, depending on the version of CPU.
Another difference is that AMD is better at gaming and Intel is better at applications and business programs. AMD chips and motherboards cost less than Intel.
Also notable is the thermal differences. Intel creates much more heat than AMD, thus making them poor candidates for over-clocking and forcing the user to take extra steps to ensure proper cooling. AMD, by comparison, generates less heat and have unlocked multipliers, making them great for over-clocking.
Choosing between AMD and Intel processors is mostly a matter of personal preference. Hewlett-Packard supports both types of processors and does not recommend one over the other.