>>328648880D have 1fps more in continuous shooting. 77D, on the other hand, have bigger buffer.
80D have AF microadjustment, if it's concerns you.
80D have 1/8000 sec shutter speed, if you ever need one.
80D have headphone port and bigger battery. Again, not really super essential stuff.
77D is lighter than 80D (~500g vs ~700g).
I was upgrading my 1100D too and went with 77D. Have nothing to complain about. Ah, and don't forget: for proper weather sealing your lenses also need to be sealed.