for me R2000i was the quintessential drafting package, but improvements in design and speed through R2004 made it a tough competition.
I didn't use R2005 and R2006 was only short lived. I still use R2007, but I don't like the quirky zooming, colorful windowing and the other eye candy that doesn't add anything to my drafting experience.
If I had to choose which one to use on a regular basis, I could probably get used to the eye candy, as distracting as it is, 2007 would probably be my choice. It has solids editing improvements over 2004 and doesn't yet implement the dreaded ribbon ... I absolutely hate the ribbon
haha .. I noticed that you didn't include R13 .. that was almost as bad as Windows ME ... or is it the other way around