All of these conical burr grinders seem to have similar motors and I wouldnt be surprised if they used the same burrs from the same factory. The most important difference between the Iberital and the Isomac is that the Isomac has a stepped grind adjustment system, whereas the Iberital has a stepless worm drive. This makes the Iberital sensational value for money, because you can dial it in exactly as you would a more expensive, stepless grinder. Stock of iberital is thin on the ground at the moment and I wouldnt be surprised if the grinder is being discontinued; I dont think that anyone makes much money out of them! We will sell them if we can get any stock; in the meantime, snap one up if you can find one (and if its where your budget is at - the more expensive Mazzers are superior).
If you still have your pressurised portafilters, I dont think that the steps will be a big deal. You should expect better coffee from unpressurised portafilters and a stepless grinder, but it will be more difficult to get a shot that looks good.
Hope that helps,