Abulia said:
Virtualization and emulation will never be as fast as running native in a dual-booting environment.
For the most part, yes, but I've read about obscure cases where it was actually faster in the virtualized environment. Most likely due to something like the host OS caching the virtual hard disk in memory.
If performance (ie. games) and stability (ie. work) are requirements for you, then dual-booting is going to be the better solution 9 times out of 10. These products (Parallels/Crossover) are nice "casual" tools that are neat to have and demonstrate, but you can't use them to play games and I wouldn't ever use them to run mission-critical apps for work.
I would argue that virtualization (but not emulation) wins on stability. Without trying to bash on Windows, virtualization allows you to run it within a clean, sandboxed environment. It does not have direct access to the physical hardware, and therefore can do less damage if something goes wrong. And more importantly for mission-critical apps, you can always backup the exact state of the virtual machine at any point in time where it's known to be configured properly and working. This is huge.
Another thing it's great for is testing applications on multiple configurations. I use Parallels to develop and test an app on Windows XP, 2000, ME, 98, Linux (various distributions), FreeBSD, and OpenBSD. All on the same Mac. Definitely more than a casual tool or demonstration. It takes computing to the next level.
Except for cases where the application needs direct access to hardware (games, demanding 3-d work like CAD, odd external devices, etc), my opinion is that virtualization beats dual boot every time. Better stability, much better ease of use (move data seamlessly between multiple environments simultaneously), faster recovery when things go wrong, etc. And for mission-critical servers, nothing beats running within VMware's industrial-strength virtualization offerings. I'm not terribly familiar with their high end stuff, but things I've read are fantastic. Like if a physical computer in a server farm fails, the virtual machine continues running uninterrupted on another computer, instant failover. Wow. Talk about stability!
Err, wait. I just went off on a complete tangent about virtualization when this thread is about emulation (Crossover). Doh!