Hydraulic Arm | Used Backhoe

Need help with hydraulic arm (10 points)?

im making a hydraulic arm (backhoe type thing) for science class at school, and im using 4 syringes and some tubing stuff, i was wondering what would be better, filling the cylinders with water or just leaaving it with air… it will be lifting light stuff nothing heavy. but which one would be more powerfull air or water.

Thanks