Canon - RF 100-500mm f/4.5-7.1L IS USM vs Tamron - 28-75mm f/2.8 Di III VXD G2

The RF 100-500mm f/4.5-7.1L IS USM is the clear pick on raw spec strength, leading by 23.5 points on the Mars Score. The margin is wide enough that the underdog only makes sense if its individual strengths line up with what you specifically need.

Pick the RF 100-500mm f/4.5-7.1L IS USM if you care most about optical stabilization / min focal. The biggest gaps in its favor are optical stabilization, min focal, max focal.

Pick the 28-75mm f/2.8 Di III VXD G2 if you carry the device everywhere and weight or thickness has been the deciding factor before. Its strongest claims are weight.

Both ship with comparable weather sealed, so those specs do not separate the two — focus on the differences below.

Bottom line: the RF 100-500mm f/4.5-7.1L IS USM is the safer default. The other model is the right choice only when its specific advantages line up with your priorities.