I like that VirtualBox is libre software, and it works for my purposes. I've used a couple of the major packages on various systems, and for my needs, VirtualBox is fine. It's been a long time since I've used vmware so I can't give a point by point critique, but the general 'feel' I get from various tech forums is vmware is a little bit better. Better's relative though. On Windows, I really liked VirtualPC for some uses. It was technically inferior to just about anything else I used, but it was fast and easy to setup for Windows on Windows. If you didn't have to do anything special, it was the quickest to get going.
As the evilsharpie said, start with VirtualBox, and see if it works for you. If it's lacking something you'd like, give vmware a try. There's also xen and kvm, but I don't have personal experience. I also second the Wine suggestion. It should be compatible, though you may need to play with settings. If so, a web search should help you out. Wine's kind of hackish, and while it can get some Windows software working for you, I wouldn't count on it to run all your favorite Windows software. It's better to find a native replacement if possible.