The pistons act perpendicular to the shaft against a cam ring, so each piston force has a long moment arm about the shaft centre. That geometry converts pressure into torque far more effectively than an axial arrangement, giving the highest torque density of the common motor types.

Smoothly, and that is their defining advantage. They develop full torque from standstill and run at a few revolutions per minute or less without the cogging and stick-slip other types show near zero speed, which is what makes them suitable for precise positioning.

Yes, at pressure and without damage, which is a genuine capability rather than a tolerance. Winches, drilling and positioning duties frequently require the load to be held rather than lowered, and a motor that can stall under pressure removes the need for a separate holding arrangement in some designs.

One where the cam ring has several lobes, so each piston strokes several times per shaft revolution. That multiplies torque and reduces speed again, producing very high torque density in a compact housing - which is why these are used on track drives and large winches.

Speed, weight and cost. They are slow by design, physically heavy, and among the more expensive motor types. Where high shaft speed is required or the duty is light, an orbital or gear motor will be far better value and considerably smaller.

Track and crawler drives, large winches, drilling equipment, marine deck machinery, and heavy positioning applications. The common requirement is very high torque at very low speed, often with the need to start under full load or hold position against it.

Both are low-speed high-torque, but a radial piston motor produces considerably more torque, runs more smoothly near zero speed and lasts longer under sustained heavy load - at several times the cost and weight. Orbital motors cover the lighter end of the same requirement far more economically.