To the original poster: why don't you just download and use both? Figure out whichever one works better for you, and buy that one when the trial periods are over.
On the topic in general, I'm kind of surprised to see such a high level of negativity towards Parallels. I've been using it for over a year now, and while it needs improvement in areas, overall I have to say it's been pretty solid. Well worth the money they earned by being over a year ahead of VMware in the Mac market.
I can't really compare the two, as I only used VMware briefly when they first came out with a beta version supporting some hardware 3-d (before Parallels supported it). The acceleration didn't work for the applications I'm interested in, so I didn't do more with it since Parallels was working fine for me.
With that said, here's a quick rundown on my pros and cons of Parallels after having used it for over a year. I'm guessing most of the pros more or less also apply to VMware, but I don't know for sure!
Pros
- Runs everything I've thrown at it, no real issues - WinXP, WinME (ack), Win98, DOS, Linux, Solaris ...
- Non-beta versions have been very stable for me on my first generation Macbook
- Access to the Windows virtual hard disk from the Mac side is a nice new feature. Mounts just like another drive while you're running.
- The latest update finally brings working hardware 3-d support for a Windows application I'm involved in developing. This is so much better than the slow software emulation!
- USB support has worked for everything I needed, including a card reader and even the built-in iSight (didn't need that, but neat that it worked).
- Snapshots are nice for when you want to try some Windows freeware but don't want it screwing with your virtual machine forever more. I used this when I needed to undelete some photos from a memory card and tried several different windows apps to find a free one that worked. You never know what dodgy stuff they install!
- Open files from either Windows or Mac in the other - ie, click on a web link on the Windows side, it opens in Safari on the Mac side. Pretty slick.
Cons
- The 1.0 series of versions seemed faster than 2.0 and 3.0. The latest 3.0 isn't as bad, but starting with 2.0, Parallels seems to use a huge disk file to cache/mirror virtual machine memory, which would sometimes slow it down considerably or even hang for a few seconds. With the 2.0 series my machine would get slower overall while running Parallels - I was seriously considering going back to the last 1.0 version when 3.0 came out and I decided just to upgrade. It's a little better. When this occasional slowdown doesn't occur, it runs nice and fast.
- Uses 15-20% CPU when the virtual machine is 100% idle. This is another thing that I felt like it didn't happen in the earliest versions, but I could be wrong.
- In version 3.0, dragging and dropping files to and from the Parallels window doesn't seem to work anymore. This was hugely convenient in 2.0. I don't know if it's just not working or if they took it away because of the new virtual disk access (which is nice, but not the same).
- No Parallels Tools support for older Windows (98, etc) or Linux.
There are some features which I don't care for just as a personal preference, including Coherence (VMware Unity) and putting Windows apps in the dock. I prefer my Windows in a separate space/window, not
that integrated with the Mac side.
I'm actually considering pre-ordering VMware if it's half as great as people here say it is, but I'm torn. Seems pretty silly to buy two different products that are so similar in overall features. There doesn't seem to be any set of features that are different enough between the two to use both on a regular basis. If I bought VMware it would be because it's clearly superior and worth the $40 pre-order. But then what if Parallels comes out with a new version that's better than VMware? Do I switch back?
Switching between the two is a bit of a pain since they don't use the same disk format.
I think I'll try the latest VMware beta before deciding whether to pre-order.