Steel stairs are without a doubt the strongest stairs with their greatest asset being that
they take a while to burn or melt in a fire. If there is a fire these
stairs will hold up the best. Steel will out last any other material if
maintained properly over time.
Steel stairs are common in large building built from steel. These buildings would include your large skyscrapers and multi level building. Some steel stairs have cement treads attached to them or steel treads with cement poured in a steel step forming a nice tread to walk on. The combination of the steel and concrete make for a very effective set of stairs in a fire.
Steel stairs also have great benefits for structural strength in different forms of fabrication. Steel stairs can be made longer and stronger than wood stairs therefore the distance between the two floors can be farther apart.
The stairway you're looking at on your left, is a new set of stairs, with two steel stringers and concrete stair tread. Attached to the concrete stair treads, is a metal hand rail or guard rail. It's hard to tell unless we measure it.
The stairway is a good example of a guard rail without a gripable handrail (or vice versa), that is between 34 and 38 inches from the stair nosing. This would be a vertical measurement, or up and down from the tip of the stair nosing, to the top of the handrail.