It can be difficult to be good. Pre-Xeno Ethics choices often result in penalties to protect native wildlife or the population. It is often better to simply take the neutral choice most of the time and pay the small amount to choose good rather than consistently choose the crippling good option.
The special defenses for good will help defend against evil psyonic weapons. The various armor types are usually more space efficient than similar area technology. However, the cost is about the same, so keep in mind you'll need a heafty economy to pay for the stronger ships. Even if you don't plan on using them, many of the techs have an added defensive bonus just for researching it, so keep an eye out for that.
The best advantage a good race has is the fact that there are four primary good races but only three of the others. This means that unless otherwise specified, there is an extra civilization to band together with if pushing for an alliance victory. As of 1.3, it is difficult (but not impossible) to form alliances with races that don't share your alignment. Thus, you are more likely to have more allies playing good than other alignments. By forming an alliance, you can get good deals from tech trading and military protection if your own military is weak.