No 2. An array of software
Is there any software in the world which the PC lacks? No, is the answer. Every major software is developed with PC as the priority.
No 1. Games
If you are a gamer, MAC is definitely not for you. There are hardly any good titles released for the MAC, while on the other hand PC arena is teeming with fabulous game titles. And, if the top titles do come to the MAC, they come in pretty late, after all the excitement has hit zero.