For example if i say: "Eu sunt puternic ca un leu". meaning "i am strong as a lion". Is this the difference between decât and ca?
"Puternic" can refer to a person's physical strength (either as the ability to lift weights or as immunity to microbes) or to emotional resilience. It can also refer to a person's influence. This adjective can also be used for abstract nouns, such as a reason to do something, an assertion, a feeling.