I'm using VMWare Fusion and its very great. I use Windows XP Pro and Ubuntu Linux with it (mainly for compiling BlitzMax programs). For Windows it supports an Unity mode too (Windows programs like OsX programs).
You could try the trials of both (Parallels and VMWare) and check what fits your requirements.
You could try the trials of both (Parallels and VMWare) and check what fits your requirements.