My second review of Fusion and Parallels appeared today in InfoWorld. I reviewed Fusion 1.0 and Parallels 3.0 a little over a year ago. They've both had major upgrades since then, so it was time for another look.

The bottom line is that there's not a lot of difference between these two products. They both perform well and do what you'd expect them to. They both have lots of cool features--especially for Windows users on the Mac--the core audience. The differences are minor. While some of those differences might be the reason that you'd prefer one over the other, they've not a reason why everyone should prefer one to the other.

I concentrated on a few things that many people want to do that can be tricky for virtualized environments: printing, 3D graphics, P2V conversions, and integration. The biggest disappoint in those areas was the graphics. My conclusion was that while both have come a long way, they're not to the point where you can get rid of your Bootcamp partition if graphics performance is important to you.

I also put together a sidebar on remote control for guest machines. Parallels introduced an iPhone app whihc is mostly a cool way to illustrate that the hypervisor has a networked API. Fusion has support for vmrun, VMWare's command line control program.

Here are a few things I wrote up as part of the review that fell on the cutting room floor:

I ran into an occasion to expand an existing drive in Fusion (one of the big benefits of virtual machines) and found the process to be easy, but slow. One catch: you can't have existing snapshots on the drive. That makes sense, but deleting a snapshot is slow work and if you've enabled auto snapshots, you might have a lot of them.

If you've going to run applications using Unity or Confluence, the guest OS---XP or Vista---doesn't matter much. XP will run almost all the software that Vista will and presents a smaller workload for the hypervisor. In Unity and Confluence, the user is opting to run Windows application in an OS X experience. Vista may not present many advantages in that setup.

Parallels 4.0 uses a different virtualized hardware stack than earlier versions. As a consequence, when you convert a Vista machine from an earlier version of Desktop, you will probably be asked to "reactivate" you copy of Vista. The problem is that the reactivation has to occur before the Parallels Tools can be loaded and the tools have to be loaded before the network will work. You're forced to do a phone activation. I've put details describing how this works in an earlier post.

Fusion supports multiple displays in full screen mode while Desktop does not. Using multiple displays is as easy has selecting an option in the "View" menu and then entering full screen.

While both products allow you to choose whether the host or guest OS should be optimized for performance, Parallels has a feature called "adaptive hypervisor" that allocates host resources on the fly based on how you're using the machine.

Both systems have made strides in making Windows installation as painless as possible---an important feature for switchers who may have never installed an operating system before. For example, both now automatically detect the OS and version from the installation disk and set reasonable defaults.