The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Tamron 16-300mm f3.5-6.3 II VC PZD and the Sigma 18-125mm F3.8-5.6 DC OS HSM for their suitability to various photography scenarios:
Size and Weight Comparison
The size of a lens is an important deciding factor when comparing two lenses. Tamron 16-300mm f3.5-6.3 II VC PZD is the longer of the two lenses at 100mm. The Sigma 18-125mm F3.8-5.6 DC OS HSM with a length of 89mm, is 11mm shorter. Besides being longer, the Tamron 16-300mm f3.5-6.3 II VC PZD also has a larger diameter of 75mm compared to the Sigma 18-125mm F3.8-5.6 DC OS HSM's 74mm diameter.
The weight of a lens is as important as its external dimensions, especially if you are planning to hand hold your camera and lens combination for longer periods. Sigma 18-125mm F3.8-5.6 DC OS HSM weighs 490g, 9% (50g) lighter than the Tamron 16-300mm f3.5-6.3 II VC PZD's weight of 540g.
Below you can find the dimension and weight table of the SuperZoom Lenses in Canon EF Mount for size comparison purposes.
SuperZoom Lenses in Canon EF Mount for Size Comparison
Lens Mounts
Both the Tamron 16-300mm f3.5-6.3 II VC PZD and the Sigma 18-125mm F3.8-5.6 DC OS HSM 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.
Tamron 16-300mm f3.5-6.3 II VC PZD is also available in Nikon F (DX) and Sony Alpha mounts.
Sigma 18-125mm F3.8-5.6 DC OS HSM is also available in Sigma SA and Nikon F (DX) mounts.
Focal Range
Tamron 16-300mm f3.5-6.3 II VC PZD has a focal range of 16-300mm and 18.8X zoom ratio which has an effective (full-frame 35mm equivalent) focal range of 25.6-480mm when used on a APS-C / DX format camera. Sigma 18-125mm F3.8-5.6 DC OS HSM has a focal range of 18-125mm and 6.9X zoom ratio which has an effective (full-frame 35mm equivalent) focal range of 28.8-200mm when used on a APS-C / DX format camera.