I think both are equally important. And you can not succeed with just one strength. Physical strength is important in sports such as cricket,football,basketball,etc. Although it focuses more on physical strength, mental preparation is required in all the sports, without mentally planning your stratergy one can not get success easily. Other sports such as chess need mental strength and zero physical strength. As we all practise makes us perfect, we need to apply this in both phycial and mental strengths in order to achieve our goals. And it also depends on the sport you choose to play. It can be outdoor and indoor. Outdoor games require more physical than mental strength whereas Indoor games require mental ability to think and no physical strength. I conculde that both the strengths are equally important.