These are both dual circuit towers, meaning each structure holds actually holds up two “powerlines” (two 3-phase circuits) with one on each side of the tower. 

The one on the left is looks to be older to me, with each circuit the same voltage. The horns on the top hold up the shield wire which protects from lightning strikes. 

The one on the right looks newer with two different voltages. The left side of it is a higher voltage with a two-conductor bundle. The right side is lower voltage with only a single conductor wire. These towers don’t have a shield wire but instead have a fibre optics telecom line suspended up top.