Thanks for the correction, did not know that
(English is not my strong subject
I think if you intent to have a single all purposes lens
to go with your camera than 18-200mm lens
is the best choice because of it wide coverage of the 3 kit lenses
. If you have the intention to invest in your lenses
collection in future, than 17-85mm is a good lens
to start with, it have a very good feel and balance with the 50D body. Personally, I would not go with 18-55mm lens
as the range is too narrow and is too light for my liking on the 50D body. Beside, you may not always have the opportunity to swap lens
when you are on the go, so having a longer range is always better.
I have both 17-85mm and 18-200mm and a 50D body, I would bring my 18-200mm with me on casual holiday and 17-85mm along with my 70-300mm for more scenic holiday or photography outing with friends. Everyone have their different photography habit, guess it is up to your personal preference.