my cruiser uses DEM 1 and 3. The powers menu in space shows identical damage bonus for both.
Duration is identical.
In performance however, I do notice the DEM 3 does more hull damage when shields are up.
Thing is.. I don't see why DEM is in the game. You dont do any serious damage to the hull while its shields are up to warrant it. You are better off using emg to wep 3 and ripping the shield out in half the time then hitting the hull darn hard.
It would be great if DEM was changed to something that makes more sense. If its directed energy modulation then it should instead either do increased damage to hull or shields (+15% @ III level) or make it increase the chance of the beam weapon secondary effect (proc) to activate and increase its effect (higher damage plasma burn, longer duration phaser disable, more debuff amount disruptor, etc).