this is a silly argument... if you're looking for gaming, then dell is the clear way to go... I am die-hard mac fan (i am posting this from my macbook), and I can admit that there aren't many games for the mac... Now if you are looking for a more media/graphic design specific environment, then the mac may be more suited to your needs...
The bottom line is PC's are better for gaming, Mac's are traditionally better for design. Another main factor is your decision is what you are used to, and whether you want to risk learning something your not used to.