For a given physical dimension (e.g. thickness or diameter), steel is stronger. For a given weight, though, aluminum is stiffer, having a higher specific modulus. There's a reason that structures needing to be rigid and light, such as airplane wings, are made of aluminum more often than steel.

Like you mentioned, there are plenty of design considerations to take into account that are material-specific. For aluminum, it's important to minimize flexing to prevent fatigue failures. Steel is much more forgiving in this regard.