Size and Weight Comparison
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 Tamron 18-270mm f3.5-6.3 II VC PZD with a length of 88mm is 12mm shorter. Besides being longer, the Tamron 16-300mm f3.5-6.3 II VC PZD also has a larger diameter of 75mm compared to Tamron 18-270mm f3.5-6.3 II VC PZD's 74mm diameter.
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. Tamron 18-270mm f3.5-6.3 II VC PZD weighs 450g, which means it is 90g (19%) lighter than the Tamron 16-300mm f3.5-6.3 II VC PZD which has a 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 Tamron 18-270mm f3.5-6.3 II VC PZD and Tamron 16-300mm f3.5-6.3 II VC PZD 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 18-270mm f3.5-6.3 II VC PZD is also available in Nikon F (DX) mount.
Tamron 16-300mm f3.5-6.3 II VC PZD is also available in Nikon F (DX) and Sony Alpha mounts.
Focal Range
Tamron 18-270mm f3.5-6.3 II VC PZD has a focal range of 18-270mm and 15.0X zoom ratio which has a 35mm equivalent focal range of 28.8-432mm when used on a APS-C / DX format camera. Tamron 16-300mm f3.5-6.3 II VC PZD has a focal range of 16-300mm and 18.8X zoom ratio which has a 35mm equivalent focal range of 25.6-480mm when used on a APS-C / DX format camera.