The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Sigma 18-200mm f3.5-6.3 II DC OS HSM and the Canon 18-135mm f3.5-5.6 IS 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. Canon 18-135mm f3.5-5.6 IS is the longer of the two lenses at 101mm. The Sigma 18-200mm f3.5-6.3 II DC OS HSM with a length of 88mm, is 13mm shorter. On the other hand, there is no difference between the max diameters of these lenses, both coming at 75mm.
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. Canon 18-135mm f3.5-5.6 IS weighs 455g, 7% (35g) lighter than the Sigma 18-200mm f3.5-6.3 II DC OS HSM's weight of 490g.
Filter Threads
The Sigma 18-200mm f3.5-6.3 II DC OS HSM has a filter size of 62mm whereas the Canon 18-135mm f3.5-5.6 IS has a 67mm diameter. Larger filters are generally more expensive than the smaller ones given all the other features are equal.
Below are links to the 62mm filters that we recommend you to consider for the Sigma 18-200mm f3.5-6.3 II DC OS HSM:
And these are the 67mm filters that we recommend for the Canon 18-135mm f3.5-5.6 IS:
Lens Mounts
The Sigma 18-200mm f3.5-6.3 II DC OS HSM has the Canon EF lens mount whereas the Canon 18-135mm f3.5-5.6 IS has the Canon EF-S lens mount. Some of the latest released cameras that are compatible with these mounts are Canon T8i, Canon 90D and Canon SL3 for the Canon EF Mount and Canon T8i, Canon 90D and Canon SL3 for the Canon EF-S Mount.
Sigma 18-200mm f3.5-6.3 II DC OS HSM is also available in the Nikon F (DX) and Sigma SA mounts.
Canon 18-135mm f3.5-5.6 IS is also available in Canon EF-S mount.
Focal Range
Sigma 18-200mm f3.5-6.3 II DC OS HSM has a focal range of 18-200mm and
11.1X zoom ratio which has an effective (full-frame 35mm equivalent) focal range of
28.8-320mm when used on a APS-C / DX format camera.
On the other hand, the Canon 18-135mm f3.5-5.6 IS has a focal range of 18-135mm and 7.5X zoom ratio which has an effective (full-frame 35mm equivalent) focal range of 28.8-216mm when used on a APS-C / DX format camera.
