Size and Weight Comparison
Size of a lens is an important deciding factor when comparing two lenses.Sigma 18-125mm F3.8-5.6 DC HSM is the longer of the two lenses at 89mm. The Sony DT 16-105mm F3.5-5.6 with a length of 83mm is 6mm shorter. Besides being longer, the Sigma 18-125mm F3.8-5.6 DC HSM also has a larger diameter of 74mm compared to Sony DT 16-105mm F3.5-5.6's 72mm 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. Sony DT 16-105mm F3.5-5.6 weighs 470g, which means it is 20g (4%) lighter than the Sigma 18-125mm F3.8-5.6 DC HSM which has a weight of 490g.
Below you can find the dimension and weight table of the 'SuperZoom Lenses in Sony Alpha Mount for size comparison purposes.
SuperZoom Lenses in Sony Alpha Mount for Size Comparison
Both Sony DT 16-105mm F3.5-5.6 and Sigma 18-125mm F3.8-5.6 DC HSM has the same Sony Alpha lens mount. Some of the latest released cameras that are compatible with the Sony Alpha lenses are Sony A68, Sony A77 II and Sony A58.
Sigma 18-125mm F3.8-5.6 DC HSM is also available in Pentax KAF3 mount.
Sony DT 16-105mm F3.5-5.6 has a focal range of 16-105mm and 6.6X zoom ratio which has a 35mm equivalent focal range of 24-157.5mm when used on a APS-C / DX format camera. Sigma 18-125mm F3.8-5.6 DC HSM has a focal range of 18-125mm and 6.9X zoom ratio which has a 35mm equivalent focal range of 27-187.5mm when used on a APS-C / DX format camera.