Well, I have been thinking about this question quite a bit. And, really, I cannot answer the question in the way it is posed. I do think that all are necessary, as you have said. But, I don't think I really like or prefer one over the other.
I most definitely prefer all of them happening at once. I find that the proper balance between them forms my most preferred state of practice. In other words, if I only had one or the other, I would be much less satisfied and probably achieve less (though I am not really too sure what exactly I am actually achieving at the moment). That is my preferred practice because I find that in this way, I experience the "perfect" amount of tension and release, inspiration, stimulation and gratification. Whenever I need more of one, I add more of that to my proportions, and that keeps the "perfection".
In the end, whatever keeps me challenged, curious, inquisitive, and in love with the music and the instrument, is what I most prefer.
m1469