Honestly I found evochron's flight model nothing like E;Ds, at least with flight assist on.
I feel they are similar enough..not a mirror image, but pretty damn similar, though nothing at all with FA OFF, EvoMerc is faster on the controls, but they both felt similar to me beyond Elite being a little slower to respond and maneuver. Elite feels smoother... EvoMerc shows its age and indie limitations in this respect though. I found that being good at one, relates into being pretty darn good at the other.
In FA OFF, Elite lets your ship move, spin, yaw, roll, etc endlessly like how it would happen in space. EvoMerc is like Star Citizen, you keep going one direction, but your directional thrusters don't let you spin at any rate...you just have a trajectory. This makes EvoMerc and SC easier to handle in unassisted mode imho. Elite can be quite the handful when you have to handle all 6 degrees and you must have a reaction for every action to prevent spinning out of control. Fun none-the-less and a challenge!
To me Elite feels like a better polished but similar FA-ON mechanics that EvoMerc has had for years now. Maybe that's just me though.