IMHO the bad guys get some phenomenal magic, lots of devastation!
It's always worth taking Saruman as his Mastery of 3 and the attack spells in "Ruin" can reduce an enemy formation very quickly. "Exssicate" then "Fire Bolt" followed by a command spell or another ruin.....awesome!
The artillery is quite effective, the Legendary formations are also very good value, the heroes are not quite so nasty, Lurtz can do some big damage to enemy heroes, while Ugluk and Vrashku can give the enemy some real surprises. Sherku's not bad either!
As for the infantry, the Orcs are okay, however you do need thousands of them, if you play sbig games you can restrict your frontage and do more damage than your opponent, (also on top of that the more formations you can take and not worry about getting them all into base contact) you can have a hero in every formation in the shape of a captain.
The good guys have some neat troops as well, Rohan have immense mogility, stay at distance and keep shooting then when you're ready dash n close, throw weapons and then charge home....devastating!
Gondor have some of the hardest hitting cavalry on the good side, Gondorian knights and knights of Dol Amroth, oh and riders of the dead
.....not to mention the legendary formation for the King of the dead, while not being mounted their special abilities means they are better than some cavalry wih their manouverability.
I haven't looked at the Trolls and Monsters too much, the hard to kill tables make them just that, the fact that you only ever get one base in combat, unless you manage to get multiple formations around them, makes them tough!
I haven't had too much experience of the Wraiths, must look in to that, I have tje models, just haven't bothered. I would imagine they rock.