Corsa, I moved right from FM3 and 4 to FM7. If you liked FM3, there's no reason to be disapointed.
Also I bought FM7 because of homologation and large list of race cars of all periods.
Homologation brings you races that looks like races, with a grid full of same era/spec cars.
It also makes cars that are not very efficient usefull and fun because they race together (4x4, luxury cars etc..)
hope this helps, watch a few let's play on youtube to be sure.