Although I don't have personal experience with either of these lenses, I would stick with the 18-200 which should be a great all around lens. There is definately too much over lap between that and the 28-300. Unless you are doing alot of wildlife photography 200mm on a dslr with a 1.6 conversion factor should be plenty long enough. And 28mm at the same conversion is not a good focal length unless you are well away from your subject (not indoors). Not to mention that the larger the difference in focal length the more sacrifices are usually made to optic quality. If you need 300mm I would look at a 75-300 which vary in quality mostly tied to price, or the Canon 70-300IS which is an awesome lens but not cheap. Or I would look at a good low light lens like Canon's 50mm f/1.8 or the more expensive 1.4 which are great portrait lenses. The 1.8 can be had for less than $80 and is extremely sharp. Or I would get a wider angle lens to compensate for the 1.6 conversion factor although they can be quite expensive.