Didn't see this before now, but I really have to say it depends on what you are trying to do with it. I am a big fan of VMware (Workstation is assumed here - but they have an entire ecosystem ranging from a simple player to a server infrastructure starting at $25K just for the licenses...), but they are definitely industrial strength software for industrial strength use (and a matching industrial strength price!).
I find VirtualBox is just about as good (yes it does support snapshotting now, and has for about 2 years). They are about 2 features behind VMware Workstation at any given time and many of those features are not as bulletproof tested as Workstation - but this is another time-tested proof of the statement that you get what you pay for. If the tradeoff is worth it to you, VirtualBox is an excellent choice.
VirtualPC 2007 is actually quite good - well considering I remember the first iteration and used it extensively as well - but very basic. If you only have basic needs and the support of Microsoft is considered benefitial to you, this is a very acceptable alternative as well.
Now for the less well known/older options –
- VMware Player - a good simple VM player. It doesn't let you create VM's or do much other than use ones others have created. However, since you typically only need to create it one time and then use it from then on - it can be acceptable in some circumstances.
- VMware Server - a corollary to Player, it has some nice feature with some significant drawbacks. Like VMware Player, it is free. However, unlike Player, you can use it to create VM's. It runs several services and has limited support for many non-server features (read none), but it can be useful for testing or for creating VM's on older machines. Otherwise you are much better off using ESXi (free) to do similar tasks.
- VMware ESXi (free) - this is a "bare metal" hypervisor. That means you install it before you install any Operating Systems on the hard drive. In effect it is the host operating system - it is just a very specialized system. The only real downside to this route that I see is it is not exactly easy to set up and get running and it has some pretty specific hardware requirements that are not easily met. That said, current new mid-range systems should have little issue. One caveat - specialized support for certain high end hardware such as graphics cards does not generally exist.
- Citrix XenServer - A citrix supported partially open-source implementation of Zen. It is effectively the same as ESXi but has a smaller ecosystem of support around it. From a technical perspective, this is my favorite in no small part because you can download a complete suite including management console and other pieces for free - up to 10 machines. It is like getting the paid version of ESX for free with the only stipulation of using no more than 10 machines. Moreover, if you are looking at Virtual Desktop Infrastructure - you can get the Citrix VDI - management suite, Server Hypervisor, and XenApp (formerly known as Citrix ICA server) all in a single package for free (again, only for up to 10 virtual machines across the entire infrastructure). It is pretty steep to get to that 11th machine though
- Parallels Virtuozzo is an entirely different way of thinking about virtualization which is not without merit, but doesn't allow you to load different OS's. It is a container virtualization scheme. In other words, you install your OS, then the software, then your programs. Each program thinks it is the only thing running in the OS because it is "contained" (depending on configuration - of course). Multiple packages can be contained within a single container as needed as well.
- Parallels also sells Parallels Desktop, which may be what you referenced, but I don’t know anything about that really other than it is comparable to VMware Fusion which in turn is comparable to a Mac version of VMware Workstation (with a lot of functionality stripped out)
I just noticed how long this got and how quick too, so I will leave it at that. I consider myself a student of virtualization so I do know a lot of things about a lot of these except how to actually use them
. I mean I know how to conceptually, but I don’t have the hardware or the money to actually play around with many of these options to learn the pros and cons first hand.
Virtualization software is a fast moving target, and just because you found the greatest thing for your situation today, doesn’t mean something new that fits even better won’t come out tomorrow (and I mean that quite literally). With that said, if you can justify to yourself VMware products, they are premiere products for a LOT of good reasons. The rest are either “Jonny come lately” or “me too” outfits that are still trying to catch VMware. If you can’t justify their products, then your options open up significantly at the cost of usability/performance/stability/features or some combination thereof.
Hope I didn’t overload you