Probably depends on what format you are rendering to. There are many HD formats. Rendering to an AVCHD file takes many time longer to render than to an mpeg format such as HDV. You will get nearly identical picture quality, but the AVCHD file will usually be MUCH smaller, sometimes close to half the size of HDV, and often supporting a higher resolution to boot.
My computer in Vegas renders HDV(.m2t) files at about double speed of normal video. Rendering to an AVCHD (.m2ts) file takse my computer about 3-4x normal speed. I have used studio in the past and I know all these options exist there as well.
