Your right the hatch did have the higher FD for some reason.
The only reasons I can think that the ex would be heavier that the hx is the sunroof and wheel/ tire combe. Well and the extra lobes on the cam shaft
Actually anyway you look at it you can't go wrong compared to what your driving now your looking at worst 14mpg more than what your getting now. That should net about $1,300 a year on the low side at 12k a year.
And Guest hello I think I know you from somewhere else