I would have to say i woudl want to improve/excell at both because you need both to be a good player you cant have one without the other at the higher levels. Each one compliments the other on court.
generally when you are young, you will have the stamina or strength. Then better focus on mental to balance it. If you are an old bird like me, it will be the other way round. Hope this helps. For older players, they will have this thought. "I wish I can be physically fit like 10 years back and has such a wisdom as now".
Both!Being a muscular player that has power n speed for the game,but no mental..useless,n also being someone that got mental as hard as steel,but no physical ability to play the game,is also useless.
actually, if they have a strong mentality, then they will have the will to improve their physical abilities. mentality is defiantly the most important.
Without the mind and the will, the body will just vegetate . Without the mind and the will, the body will just vegetate. .