I would say if you want to start work on video and are fairly new or somewhat proficient, iMovie is where you should go. I've seen iMovie in action (as I'm sure many others here have also) and it's a dream compared to Windows Movie Maker. Plus, you will be working with QuickTime as well, which in my opinion is a better product for audio and video.
If you are looking for something a little more advanced, there's also the Final Cut series of products for video production.
It's also ideal for 3D rendering with Maya and other packages out there.
Aside from all that, you will be working on a robust, reliable operating system based on UNIX under the hood. You will also have one of the sexiest laptops on the planet.

Seriously though, I would stick with the Mac. Consider also that the 15 and 17 inch PowerBooks also come with FireWire 800 (IEEE-1394b) as well as the regular FireWire 400 (IEEE-1394a) for lots of data throughput. USB 2.0 is also included.
One last thing. Remember that Apple's Macs for the most part hold their worth for a much longer time than PCs with Windows do. I still see people going around with the older PowerBook G3 laptops.
Heck, I even have an old circa-1993 Apple Macintosh Quadra 650 (pre-PowerPC Motorola 68040 CISC-based CPU running at 33 MHz; Mac OS 8.1 installed on a 9 gig SCSI drive; 112 MB RAM) hosting my family website!! Now if that isn't a testament to the Mac's staying value, I don't know what is! ::angel::