We are planning a trip for November of this year and before that we would like to get a new lens for our camera. We have a Canon Rebel XTi, with the standard 18-55mm lens and a Promaster 70-300mm lens. Neither one of these lenses have any image stabilizer and we are tired of changing out the lenses. We have a budget of under $600 for a new lens and have narrowed it down to the Sigma 18-200mm and the Tamron 28-300mm, both with image stabilization (OS for Sigma and VC for Tamron). We like the wide angle of the Sigma and the long focal length of the Tamron. This will be our main lens for the camera, not just for Disney trips. Would what we gain in the 18-28 range offset what we lose in the 200-300 range if we get the Sigma and vice versa for the Tamron? We would like to solicit any comments or experiences that anyone may have regarding these lenses or setups. Thanks.