The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Tamron AF 18-200mm f3.5-6.3 XR II LD and the Sigma 70-300mm F4-5.6 DG for their suitability to various photography scenarios:
Size and Weight Comparison
The size of a lens is a crucial factor to consider when comparing two lenses. Sigma 70-300mm F4-5.6 DG is the longer of the two lenses at 122mm. The Tamron AF 18-200mm f3.5-6.3 XR II LD with a length of 84mm, is 38mm shorter. Besides being longer, the Sigma 70-300mm F4-5.6 DG also has a larger diameter of 77mm compared to the Tamron AF 18-200mm f3.5-6.3 XR II LD's 74mm diameter.
The weight of a lens is equally significant as its external dimensions, particularly if you intend to handhold your camera and lens combination for extended periods. Tamron AF 18-200mm f3.5-6.3 XR II LD weighs 398g, which means it is 152g (27%) lighter than the Sigma 70-300mm F4-5.6 DG which has a weight of 550g.
Filter Threads
The Tamron AF 18-200mm f3.5-6.3 XR II LD has a filter size of 62mm whereas the Sigma 70-300mm F4-5.6 DG has a 58mm diameter. Larger filters are generally more expensive than the smaller ones given all the other features are equal.
Below are links to the 62mm filters that we recommend you to consider for the Tamron AF 18-200mm f3.5-6.3 XR II LD:
And these are the 58mm filters that we recommend for the Sigma 70-300mm F4-5.6 DG:
Lens Mounts
The Tamron AF 18-200mm f3.5-6.3 XR II LD has the Canon EF lens mount whereas the Sigma 70-300mm F4-5.6 DG has the Nikon F (FX) lens mount. Some of the latest released cameras that are compatible with these mounts are Canon T8i, Canon 90D and Canon SL3 for the Canon EF Mount and Nikon D6, Nikon D780 and Nikon D3500 for the Nikon F (FX) Mount.
Tamron AF 18-200mm f3.5-6.3 XR II LD is also available in Nikon F (DX) , Sony Alpha and Pentax KAF mounts.
Sigma 70-300mm F4-5.6 DG is also available in Canon EF , Nikon F (FX), Pentax KAF, Sony Alpha, Sigma SA, Canon EF, Pentax KAF, Sony Alpha and Sigma SA mounts.
Focal Range
Tamron AF 18-200mm f3.5-6.3 XR II LD has a focal range of 18-200mm and
11.1X zoom ratio which has an effective (full-frame 35mm equivalent) focal range of
28.8-320mm when used on a APS-C / DX format camera.
On the other hand, the Sigma 70-300mm F4-5.6 DG has a focal range of 70-300mm and 4.3X zoom ratio . When it is mounted on an APS-C sensor camera with 1.5x crop, it provides a 35mm (FF) equivalent of 105 - 450mm.