No offense to you, mcatt66, but I really wish people would stop asking this question. They're really for two different contexts completely, and the question implies that they're mutually exclusive -- but they're not, you can have both. It's like asking "a car or a plane?" Well, both allow you to travel, but it's the point of the trip you have to consider.
Boot Camp is free, so you can have that no matter what. Parallels allows you to run Windows apps right along with your OS X apps, which is invaluable for me especially with Coherence mode. There is no reason for me to use Boot Camp unless I want to play a 3D Windows-only game. Just like there's no reason for me to use a plane unless I'm going someplace really really far away. Do you have ANY Windows app that you want to use regularly that's not a game? If so, buy Parallels, because do you really want to be constantly rebooting just to use one or two programs? No, that's time consuming and inconvenient; in my travel analogy, it's like going through the hassle of an airplane trip (with getting to the airport, security, etc) when you only need to travel 100 miles.
In short: you'll probably want to use both. If you're using Parallels, you might as well install Boot Camp too because Parallels can use the Boot Camp partition.