Generally, I - beams have a higher load - bearing capacity in the direction of the web due to their more symmetrical cross - section, which distributes loads more evenly. Channel steel, with its U - shaped cross - section, has better performance in resisting lateral bending and torsional loads in some cases. When the load is mainly vertical and acts along the axis of the beam, I - beams are usually more suitable. But when there are significant lateral forces or when the structure requires more resistance to twisting, channel steel may be a better choice. The actual selection depends on the specific engineering requirements and load conditions.