Control monitors are voiced a little more bassy, since they're usually made to sit on top of a console (hence, 'control') when recording is taking place... they're out in open space, and therefore cannot get any "bass reinforcement" from a wall.
That said, if you put the 4312 on a stand, and place it a few feet out from a wall, you can duplicate the intended environment pretty well, and they balance out well.
And yes... the 4312 is much improved over the L100. If nothing else, the 4312 has a real tweeter (035Ti, as opposed to the severely limited LE25 cone tweeter in the L100 and 4311)...
Regards,
Gordon.