VMware Fusion is competitive product to Parallels. I use it to run SolidWorks on an iMac i7 and it runs very well but, certain little thing behave strangely on it. e.g. CTRL selecting entities seems to behave strangely. The other strange thing is that while SolidWorks itself runs very well with 3D accelerated graphics mode, I have a plug-in that doesn't work correctly with that enabled.
Bootcamp will run SolidWorks very well in a pretty much native fashion. If you have room on your hard drive, I would recommend making a bootcamp partition for windows/solidworks and then add VMware fusion (or parallels) so that you can access it in "emergencies". Trick is, you have to install the bootcamp version first and then import it into VMware.
Realize that when you run bootcamp, you'll have no access to OS X.
-Andy B.
http://www.birkonium.com CNC for Luthiers and Industry http://banduramaker.blogspot.com