This quote is saying that it is better to be strong and capable than to be attractive but not able to do anything helpful. Being strong can mean many different things depending on the context. It could mean being physically strong, having emotional resilience, having sound judgement, or just generally having the ability to take action and accomplish goals. In other words, it is better to have skills and strength which allow you to make a difference in the world than to have looks but not be able to do anything beneficial.