The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Sigma 18-300 F3.5-6.3 DC OS HSM and the Tamron AF 18-270mm f3.5-6.3 II VC LD 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 18-300 F3.5-6.3 DC OS HSM is the longer of the two lenses at 102mm. The Tamron AF 18-270mm f3.5-6.3 II VC LD with a length of 101mm, is 1mm shorter. On the other hand, the Tamron AF 18-270mm f3.5-6.3 II VC LD has a larger diameter of 80mm compared to the Sigma 18-300 F3.5-6.3 DC OS HSM's 79mm 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 18-270mm f3.5-6.3 II VC LD weighs 560g, 4% (25g) lighter than the Sigma 18-300 F3.5-6.3 DC OS HSM's weight of 585g.
Below you can find the dimension and weight table of the SuperZoom Lenses in Canon EF Mount for size comparison purposes.
Super Telephoto Lenses in Canon EF Mount for Size Comparison
Filter Threads
Both the Sigma 18-300 F3.5-6.3 DC OS HSM and the Tamron AF 18-270mm f3.5-6.3 II VC LD have the same Filter thread size of 72mm.
Below are links to the 72mm filters that we recommend you to consider for these lenses:
Lens Mounts
Both the Sigma 18-300 F3.5-6.3 DC OS HSM and the Tamron AF 18-270mm f3.5-6.3 II VC LD has the same Canon EF lens mount. Some of the latest released cameras that are compatible with the Canon EF lenses are Canon T8i, Canon 90D and Canon SL3.
Sigma 18-300 F3.5-6.3 DC OS HSM is also available in Nikon F (DX) , Pentax KAF3, Sigma SA and Sony Alpha mounts.
Tamron AF 18-270mm f3.5-6.3 II VC LD is also available in Nikon F (DX) mount.
Focal Range
Sigma 18-300 F3.5-6.3 DC OS HSM has a focal range of 18-300mm and
16.7X zoom ratio which has an effective (full-frame 35mm equivalent) focal range of
28.8-480mm when used on a APS-C / DX format camera.
On the other hand, the Tamron AF 18-270mm f3.5-6.3 II VC LD has a focal range of 18-270mm and 15.0X zoom ratio which has an effective (full-frame 35mm equivalent) focal range of 28.8-432mm when used on a APS-C / DX format camera.