Hi Trinity
You used the term "upgrade" which could mean many things to many people. I assume you have the Canon Kit Lens 18 - 55mm. So it really depends on where you find the kit lens lacking.
On the image quaility front I doubt either of these lens are any better than the kit lens. They will give you an extended zoom range of x10 over the the x3 range of kit lens. Which can be very useful and versertile for a one lens solution travel - walk about lens.
With the Canon crop factor of 1.6 they lens will have a 35mm equivalent of
18 - 200mm = 29mm - 320mm - wide angle view to telephoto view
28 - 300mm = 45mm - 480mm - normal view to extreme telephoto
If you photography building and landscape then you will need the 18mm end of the range and the 300mm for small distant wildlife. I agree with Duncan that the 18 - 200mm is most likely to suit your subjects.
From a Quality point of view both lens score about 5/10 or 6/10. which is much the same as the kit lens. They seem to perform better when stopped down to f8 - f11 and give better image sharpness in the centre of the frame compared to the edge of the frame. Image distortion is another worry with wide range zoom lens.
A review of the 18-200mm
http://www.photozone.de/8Reviews/len...3563/index.htm
Zooms with a x10 range are best avoided because you have to spend a lot of money to overcome design compromises. This is why x3 zooms are much cheaper and generally give better image quaility.
If you want a wide zoom range for a walk about lens and always crop from the centre of the frame then go for it.