Hydraulic machines are typically slower, heavier, and require larger HP engines than a mechanical drive. Maintenance would be minimal, depending on the final drive design. An oil cooler would be needed, heat thins and breaks down the fluid, and can hurt pumps and motors quickly. A hydraulic machine will give a great amount of control, and almost instant torque.
There are advantages and disadvantages to any design, you need to choose based on your needs.
I don't want to go fast, I just want to go anywhere.