Neutral gets Neutrality Learning Centers for fast research, Neutral Shipping for those who like trade(like me), totally free terraforming(no tech required) and discounts on core ships(which can be used to buy them cheap and sell them to other races at higher prices). Neutral ethical choices have hardly any or no effect on the game at all.
Evil gets the ridiculously overpowered Psyonic Beam, the similarly exaggerated Psyonic Shredder, the comparatively tame Psyonic Missile, and those aforementioned cheap-o Galactic Achievements which reduce game difficulty. The Evil ethical options are disgusting if you actually read them, but make your game easier for no input effort.
Good gets improved defenses like Subspace Rebounders, Dynamic Shielding, Telepathic Defense, and the very nice Arnorian Battle Armor. However, except for Arnorian Battle Armor, the other special defenses are not quite as overpowered as the Evil alignment's Psyonic weaponry is. As for Achievements, the only decent one that the Good alignment gets is the Empathic Tactical Center which increases all your ship defenses by 20%. The Good ethical options are largely self-destructive drawbacks in the name of being a good ruler.
I'm Neutral because of the automatic terraforming, NLCs, Neutral Shipping and ship discounts. The other two alignments may get special stuff to put on their ships and planets, but technology can always be traded and planets can always be conquered.