The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Sigma 90mm F2.8 DG DN C and the Fujifilm XF 90mm F2 R LM WR 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. Fujifilm XF 90mm F2 R LM WR is the longer of the two lenses at 105mm. The Sigma 90mm F2.8 DG DN C with a length of 60mm, is 45mm shorter. Besides being longer, the Fujifilm XF 90mm F2 R LM WR also has a larger diameter of 75mm compared to the Sigma 90mm F2.8 DG DN C's 64mm diameter.

Fujifilm XF 90mm F2 R LM WR vs Sigma 90mm F2.8 DG DN C Lenses Size Comparison
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. Sigma 90mm F2.8 DG DN C weighs 295g, which means it is 245g (45%) lighter than the Fujifilm XF 90mm F2 R LM WR which has a weight of 540g.
Filter Threads
The Sigma 90mm F2.8 DG DN C has a filter size of 55mm whereas the Fujifilm XF 90mm F2 R LM WR 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 55mm filters that we recommend you to consider for the Sigma 90mm F2.8 DG DN C:
And these are the 62mm filters that we recommend for the Fujifilm XF 90mm F2 R LM WR:
Lens Mounts
The Sigma 90mm F2.8 DG DN C has the Sony E lens mount whereas the Fujifilm XF 90mm F2 R LM WR has the Fujifilm X lens mount. Some of the latest released cameras that are compatible with these mounts are Sony FX5, Sony A7R VI and Sony A7 V for the Sony E Mount and Fujifilm X-T30 III, Fujifilm X-E5 and Fujifilm X-M5 for the Fujifilm X Mount.
Sigma 90mm F2.8 DG DN C is also available in the Leica L mount.
Focal Range
Both lenses have the same focal range of
90mm but while Sigma 90mm F2.8 DG DN C has the fastest aperture of
F2.8, the Fujifilm XF 90mm F2 R LM WR's widest aperture value is
F2.0.