[m3ch4num470r]

In terms of efficiency for a single movement, motors are more efficient than pneumatics. This is because your compressor is driven by a motor which gives it all the inefficiencies of a motor drive. Add this to the fact that as air pressure increases, it becomes harder and harder to compress and you get a system that uses significantly more power (and weight) than a simple motor drive.

However, I am unaware of a team that has killed its battery in 2 minutes of competition. You should probably be looking at the other features of each. Motors have more than two positions, but that isn't necessarily a disadvantage. With a cylinder, you will be reliably able to hit the two posistions, while a motor may need additional controlling systems (like a potentiometer or wheel encoder). Also, pneumatics give you holding power while a motor may slide under load. After a cylinder is energized, you don't have to add any extra power to keep it in its position, while a motor may need constant pulsing to keep it even close to where you want it. Finally, you have to consider weight since adding a compressor and 4 air tanks is a lot of extra load. My team was considering not using pneumatics just because of the weight, but our designs made pneumatics a whole heck of a lot more convenient.

Bottom line is there's a lot more to consider than pure energy efficiency.