The Era is more on par with the S100, not the S80, so that might be a better comparison to make.

Functionally, both the S100 and Era do the same things except the Era also has wifi capability and the option to connect to the Spot tracking network.

However, since you already have the GPS in the flarm, the S80 makes sense instead of the S100. You lose the back-up battery feature going to the S80 from the S100, but you also save a bunch not buying the second GPS and recorder. The Eos 80 gives the back-up function as well as built-in bluetooth and GPS/ IGC recorder.

All of them have optional AHRS add-ons, but unless you have an Instrument rating you shouldn't buy or use an AHRS to cloud fly.

Any one of the 4 options would be good, with the S80 coming in at the lowest price to do what you want it to do.