This depends on what you mean by 'better'. If by 'better' you mean stronger, then steel wins. If by better you mean 'safer', then concrete probably wins as steel doesn't hold up well when exposed to fire.
Both materials are appropriate and valid structural materials. Determining which one to use will depend on your personal project goals but usually, it comes down to three factors: Time, space, and cost.
Structural steel constructions can be completed faster as the construction is less messy and the material is lighter. It also takes up less space. However, it comes at a higher cost as the material is more expensive and you have to pay for the fabrication process. Concrete lacks these benefits but is much cheaper so if cost is a priority then concrete may be the best option.
The 'best' option will depend on what your priorities are. For example, during the construction of my own property, I decided to find a company offering structural steel fabrication in Kent as time was the most important factor for me and I really wanted to maximise the space available.