The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Sigma 18-250mm F3.5-6.3 DC OS HSM and the Tamron 18-270mm f3.5-6.3 II VC PZD 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 18-250mm F3.5-6.3 DC OS HSM is the longer of the two lenses at 89mm. The Tamron 18-270mm f3.5-6.3 II VC PZD with a length of 88mm, is 1mm shorter. On the other hand, there is no difference between the max diameters of these lenses, both coming at 74mm.
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 18-270mm f3.5-6.3 II VC PZD weighs 450g, 4% (20g) lighter than the Sigma 18-250mm F3.5-6.3 DC OS HSM's weight of 470g.
Below you can find the dimension and weight table of the SuperZoom Lenses in Nikon F (DX) Mount for size comparison purposes.
Super Telephoto Lenses in Nikon F (DX) Mount for Size Comparison
Filter Threads
The Sigma 18-250mm F3.5-6.3 DC OS HSM has a filter size of 72mm whereas the Tamron 18-270mm f3.5-6.3 II VC PZD has a 62mm diameter. Larger filters are generally more expensive than the smaller ones given all the other features are equal.
Below are links to the 72mm filters that we recommend you to consider for the Sigma 18-250mm F3.5-6.3 DC OS HSM:
And these are the 62mm filters that we recommend for the Tamron 18-270mm f3.5-6.3 II VC PZD:
Lens Mounts
Both the Sigma 18-250mm F3.5-6.3 DC OS HSM and the Tamron 18-270mm f3.5-6.3 II VC PZD has the same Nikon F (DX) lens mount. Some of the latest released cameras that are compatible with the Nikon F (DX) lenses are Nikon D3500, Nikon D7500 and Nikon D5600.
Sigma 18-250mm F3.5-6.3 DC OS HSM is also available in Canon EF , Pentax KAF3, Sony Alpha, Sigma SA, Canon EF, Nikon F (DX), Pentax KAF3, Sony Alpha and Sigma SA mounts.
Tamron 18-270mm f3.5-6.3 II VC PZD is also available in Canon EF mount.
Focal Range
Sigma 18-250mm F3.5-6.3 DC OS HSM has a focal range of 18-250mm and
13.9X zoom ratio which has an effective (full-frame 35mm equivalent) focal range of
27-375mm when used on a APS-C / DX format camera.
On the other hand, the Tamron 18-270mm f3.5-6.3 II VC PZD has a focal range of 18-270mm and 15.0X zoom ratio which has an effective (full-frame 35mm equivalent) focal range of 27-405mm when used on a APS-C / DX format camera.