Using Boot Camp vs. Straight Parallels 4.0

I am running Parallels 4.0 (latest build) on a MacBook Pro 17 with Snow Leopard and the latest update. I installed Windows Vista Ultimate x64 (SP1) using the 3 step installer wizard. Everything seems to be working fine.
My question is: Is there a difference using Parallels alone vs. using it with Boot Camp? I do not seem to understand the distinction. Any education you can provide would be truly appreciated.

 

Basically, if you are using Parallels virtual machine based on a Boot Camp partition you can always boot directly into Windows (natively). This could be useful if you need to run some specific program that would not run in virtualized environment.

There are some limitations however (taken from documentation):

"There is a number of limitations for a Parallels virtual machine that uses the Boot Camp Windows partition either as a bootable volume or as a data disk:

* it cannot be suspended or paused
* such a virtual machine cannot have snapshots and the Safe Mode feature cannot be enabled for it
* compression or compacting cannot be performed

Note: In Parallels Desktop 4, there is no limitations on types of users who can access the Boot Camp Windows partition from a virtual machine. You can log into Windows even if you don't have administrator rights."