The 80d has the following feature set upgrades to the Rebel t5i
- Faster and more accurate auto focus.
- Auto white balance more accurate. Better colors.
- Advanced WB features such as auto WB White priority and setting Kelvin.
- Overall Higher ISO performance much better - ISO 3200 works on both the rebel and the 80d - but looks much cleaner on the 80d.
- For my 1.4 lenses - MF adjustments - +5 improved my canon EF 50mm 1.4 greatly.
- Better overall exposure and dynamic range - less extreme between shadows and light.