Well,I think we can hardly lose one of them.To a healthy person,losing the former or the latter might cause serious problem.
But,in this way,mental health may be more important.We can think in a opposite way.There is two person,one is only with mental health and the other one is only with physical health.So obviously the former can be happy but the latter can not.
sorry,My English is just so-so.That's just some opinion of mine.Hope they can give you a hand..
Thanks.