Which one is better, Nikon D500 or Canon 80D?

The Nikon D500 is better. The D500 is a flagship APS-C format SLR, while the EOS 80D is a mid-range APS-C SLR. The difference between the two is not the slightest, just like the comparison between a family car and an off-road SUV. The D500 is designed for high-speed/high-intensity shooting in harsh outdoor environments and sports photography, while the 80D is designed for home use. The reliability and stability, dustproof and splashproof performance, and mechanical strength of the fuselage are not at the same level. Among Canon APS-C SLRs, only the 7DII can barely compete with it.