MM1 -> MM2
Two basic changes: Elite and solo defences pulled down to those of monsters their level and solos having their hit points cut from five times normal to four. Damage increased in both cases to compensate. Also no really unfun monsters in the MM2 such as the Purple Worm (no damage, just a great sack of hitpoints), the Dracolich (All Stun, All the Time) or the Wraith (insubstantial + imposing weakness + regeneration = one tedious to kill monster).
MM2 -> MM3/MV
Monster damage increased significantly. Brute and Soldier to hit bonusses brought into line with other monsters of their level. Lurkers revamped.
MM1-> MV (additional)
Level 1 solo dragons and lower level ogres and other creatures brought in. Monster design generally improved (a few nerfed like the hexer) and the bad monsters such as the three mentioned above given a significant overhaul.
