Funny thread.... "Mine is bigger than yours" I have often heared in playschool...
I know a lot of so called pros using prime lenses. However, many pics of these guys are just crap and I would never put them online.
Why not use the 18-200? First of all I can only recommend to test it if possible. Forget Ken Rockwell, forget the numerous tests. Pictures are always very subjective, what the testers may like could be crap in your eyes. So go and talk to 18-200VR - users and look at their pictures. Find out if they're a treated or not. Consider what for you will need the lens, if the speed and AF-speed is okay for the pics you want to shoot.
If all is okay go and get the darn thing if you like it and do not listen to what self proclaimed specialists tell you.
If this does not help you read what buckphotography wrote. And read it again and again
Just a hint, consider the 55-200VR if you do not need the range between 18 and 50MM. It makes even better pictures than the overall good 70-300VR, only the AF is remarkably slower....
Regards
S.