CAD: Parallels 4 or Bootcamp?

For graphic intensive programs like Solidworks (CAD) or 3D StudioMax run on the guest XP OS, i'd prefer to use Parallels 4 and eliminate the need for Bootcamp. would there be any noticeable drop-off in speed? Do i still need Bootcamp?

 

Use both, since Parallels can use the Boot Camp partition.