Every robo has a style as well as a model. The style distinguishes among robos of the same model. There are three robo styles.

Power
The robo has about 5% extra attack power. While enemies take more damage, there is slightly more risk in crashing into your own bombs/pods. Good for strengthening any weak weapon.

Speed
Robos of this type generally have higher ground speed and aerial maneuverability. Perfect for dodging gun rounds.

Armor
Increased defense and/or endurance. Less damage taken and more damage endured. These types are slightly more cumbersome.