Canon - RF 100-500mm f/4.5-7.1L IS USM vs Tamron - 150-500mm f/5-6.7 Di III VC VXD

These two are nearly even on the Mars Score (80.6 vs 83.2). The decision isn't about overall quality — both clear the bar — it's about which specific trade-offs fit your use.

Pick the RF 100-500mm f/4.5-7.1L IS USM if you carry the device everywhere and weight or thickness has been the deciding factor before. The biggest gaps in its favor are weight.

Pick the 150-500mm f/5-6.7 Di III VC VXD if you care most about min focal. Its strongest claims are min focal.

Both ship with comparable max focal, weather sealed, optical stabilization, so those specs don't separate the two — focus on the differences below.

Bottom line: there is no wrong answer here — match the spec advantages to how you actually use the product. The Mars Score parity tells you both are well-rounded; the differences are about trade-offs, not quality.