For example there are lots of PDF converters. Some are good and return fidelity to the original with much reduced file size. Others return a PDF with grossly enlarged file size.

So what, in this case, will be the performance factor?

Good? Or possibly lethargic?

It's a great idea, but it doesn't run on Linux. Let's hope that changes soon.

VMware has been involved in server virtualisation for years, and they are _very_ good at it. Parallels is going to have to move on price rather quickly I suspect, or they are going to be owned.

I have been trying/testing both and Fusion doesn't run my fans at 6000rpm after 1/2 an hour...parallels seems to run better when it's on battery, but Fusion seems to run cooler whenever and doesn't crank up my CPU anytime.

Oh and it's unity view is way cooler than Parallels version IMHO

Completely misses the key differentiator between Parallels and VMWare in not commenting on the Unity feature. Unity lets you use an application inside a VM in "seamless" mode, in a similar way to the way Citrix provides published apps. It also lets you put Apps from inside a VM onto the Dock so you can call them directly without having to go through the polava of having to launch the VM first.

I think this is possibly the best feature that Unity has, it allows you to have a windows app and a mac app side by side and do copy and paste between the two without minimising or using awkward key combinations to jump between the VM and the host.

and Fusion knocks the socks off of Parallels. Parallels (and VirtualBox, an open source contender) hammer the processors when booting Windows, and indeed doing anything more complex than running Firefox, but VMWare just takes a share of the processor like any other application (about 20% on boot) and barely changes while running any application. Unity allows Windows apps to run on the OS X desktop with little perceivable hit to performance. To be honest I only use it for website compatibility testing but IE, Firefox and Opera all perform well. It's definitely worth $39.

depends on the hardware used. If the cpu supports virtualization, then the performance drop is minimal, due to the hardware based solution. (much like the v86 mode /dos window/ was implemented in windows) For older cpus without virtualization support, the best what you can get is half speed with some graphics performance problems. The only catch is that the eula of vista prohibits people from running the ultimate versions of the os on a virtualized platform.

"Performance..." poster has it wrong.

got it backwards. Ultimate is the only Vista OS that is licensed to run on Virtual computers.

From the Vista EULA:

VISTA HOME BASIC & HOME PREMIUM:

USE WITH VIRTUALIZATION TECHNOLOGIES. You may not use the software installed on the licensed device within a virtual (or otherwise emulated) hardware system.

VISTA ULTIMATE:

USE WITH VIRTUALIZATION TECHNOLOGIES. You may use the software installed on the licensed device within a virtual (or otherwise emulated) hardware system on the licensed device. If you do so, you may not play or access content or use applications protected by any Microsoft digital, information or enterprise rights management technology or other Microsoft rights management services or use BitLocker. We advise against playing or accessing content or using applications protected by other digital, information or enterprise rights management technology or other rights management services or using full volume disk drive encryption.

But it's called "Coherence". Windows apps in the Dock, Mac apps in Windows, and all windows together on the same desktop...

http://uk.youtube.com/watch?v=rN9jNNeEd98

I've not delved into Fusion, but it sounds the same to me.

Where did you get that fact? It even works for running 64bit linux in smp, neither of which parallels can do.