I think they are both good, but Parallels might be slightly more refined for the Mac. I remember watching a video benchmarking a MBP recently, and the reviewer noted that taking (or maybe it was restoring) a snapshot under Parallels was much much faster than under VMWare.
Parallels releases a new update every year, which usually you can get for $40 or $50 discounted. But they support new Mac OS's two years back, so you really only need to spend $20-$25/yr to keep it working, which to me is a reasonable deal.