the freeride's have the shock absorber in the bootboard, the regular 80's don't. also, the cuff is lower on the freerides, which technically makes them a little softer flexing.
The FRs are great boots. I've never felt shin or heel bang. Best boots I've ever ridden. I would recommend them if you're on the small side. Otherwise, go with the 100FRs or the 120FRs.
the flex index number on Langes indicates that a 120=120 and 80=80
in any given flex range a FR120 and a Comp 120 are as stiff as each other but the FR boot is made with a more lastic material that doesn't force you right back upright when you flex the boot like the blue race boots do
the same goes for any model of Lange where there is a FR and regular version
as mentioned above there are lower cuffs and shock absorbers too