Which kind of ball-rubber or steel-will bounce higher?

If the balls are the same size, and the thrown with equal force on a pavement, then the steel ball will bounce higher.

What determines the bounce of a ball is the speed with which it returns to its shape after it has been compressed on impact. This return to shape is what forces the ball up into the air. Rubber compresses very easily, but it is fairy slow in returning to shape. Steel compresses quickly, and returns to its shape very rapidly.