Sigma 100-400mm f/5-6.3 DG DN OS is definitely the best choice for Canon EOS R6 Mark III. The bokeh is beautiful The low distortion is perfect for professional photography.

Why this lens? The image quality convinces in all tests - both for photography and for video. Unbeatable for the price, can only recommend. Have already done several projects with it, always satisfied. Also more than sufficient for demanding tasks.

Using Canon RF 100-500mm f/4.5-7.1L IS USM for a few months for Canon EOS R6 Mark III and can only recommend it. The sharpness is extremely high The low distortion is perfect for professional photography.

Switched to Sigma 100-400mm f/5-6.3 DG DN OS about a year ago and am thrilled. The price-performance ratio is great The ergonomic design allows for comfortable handling.

My clear recommendation for Canon EOS R6 Mark III: Canon RF 100-500mm f/4.5-7.1L IS USM. The weight is manageable and comfortable The low distortion is perfect for professional photography.

Technical highlights: The latest generation offers significantly better image quality. Very good compatibility with Canon EOS R6 Mark III features. Can be used without problems for various photography styles. Even after hours of shooting, no performance losses. Very good build quality, even at high usage.

For Canon EOS R6 Mark III Canon RF 70-200mm f/2.8L IS USM fits best. The sharpness is extremely high The fast autofocus makes everything feel responsive and accurate.

Would definitely take Canon RF 70-200mm f/2.8L IS USM for Canon EOS R6 Mark III. The bokeh is beautiful The low distortion is perfect for professional photography.

For Canon EOS R6 Mark III I would take Sigma 100-400mm f/5-6.3 DG DN OS. Best choice currently.

Man I wish I found this thread sooner. Would have saved me so much hassle.

Seconded!

Basically, looking at the thread so far, it seems like there's a pretty clear divide between prioritizing reach with those 400-500mm options and prioritizing speed with the f/2.8 zoom. TBH, it kinda depends on what sport your actually shooting. I've gotta agree with the point about the 70-200mm being a beast—that fast aperture is a lifesaver for indoor games where the light is usually garbage (at least that's how it is at my local gym). One thing to keep in mind with the R6 Mark III is how the lens communication handles the higher burst rates; sometimes 3rd party glass can lag just a tiny bit compared to native RF stuff when *really* pushing the tracking, though I'm not 100% sure if the latest firmware fixed that entirely. Honestly, it's all about that trade-off between reach and light-gathering capability. If you're on the sidelines of a dimly lit court, you'll definitely want that wider glass over the extra focal length.