depends on whether you need the extra range 105-200mm.
In my opinion, it's not really necessary. But of course it depends on what type of photography you like.
I'm not sure what the image quality difference is between the 2 lenses. I know the price is greatly different!
18-200 have mechanical flaw that will eventually spoil the lens. Just go ahead with the kit lens, if not buy the 24-70 f/2.8 or 17-55 f/2.8 that will cost you a bomb but realistically get the Tamron 17-50 f/2.8 if you don't like the kit lens.