I'm not going to even get into the great which is better PC or Apple debate here.
In order to make your machine more capable in the image and video department, the first thing I would do is get some more RAM. 512MB is good, but a GB or more is better. That will help with the speed issues (a little).
Also, onboard storage. The more hard drive space the merrier when it comes to video handling. I have about a Terabyte worth of hard drive space that I work with when it comes to editing videos. Makes things go a lot easier come production time.
As for the differences between Macs and PCs, that can be debated until the cows come home. Bottom line is that different people prefer different things based on their experiences. PCs and Macs can both do the same things with equal proficiency. Macs are designed as art based computers (meaning they are built to handle images, video, and the like) and are ideally suited for handling applications of a graphic nature. PCs are primarily designed as office computers and handle those type of applications quite well. Over the past few years both machines have made great strides into the others arena in order to attrack a more diverse crowd. You can now find PCs that handle graphics on the same level as Macs and Macs that handle office applications on par with PCs.
The problem comes in distribution. PCs own the market and thus control the hardware and software supply. You can find Mac stuff if you know where to look, but as Error mentioned...selection is not great, diverse, or huge at the local computer stores (Best Buy, CompUSA, etc.)
I personally run PowerMac computers at home/personal use and the Navy provides me with medium to high end Dells at work. I prefer the Macs.
