i am now of the philosophy that the least possible effort will gain you the same sound! it's levers all the way. sometimes when i find a space of 1/4 to 1/8 inch between fingertips and tops of piano keys - i try to go back to the 'massage' way of playing. also, my forearms are completely relaxed and it's just kind of like massage actually. you wouldn't work from a foot above a person to hit their back or massage. you'd do little movements very close to them and use the friction and heat that is involved with very small movements done very quickly. wierd comparison probabaly - but there's this intense 'heat' that can come from the mind and not so much the physical outward manifestation of the 'work' of playing the piano. it's really not much work at all. when you practice this way.
also, i've been learning about extraneous sounds that you don't want from too overt movements. ie key slap, buzzing bass notes. if you don't have any space between fingertip and key - there is no extraneous sound from tapping the notes. you'll hear this with some fast bach pieces (slap slap slap). also, if you press bass notes - just to the point that you hear a good tone - it sounds much better than bZZZZZZZZZ vibrating around the tone.
*about the forearms. i used to use them a lot to start and end passages. now, it's sort of like they are just there. they follow the fingers around and are basically there to steady the hands and create a visual 'flow.' i feel a sort of impulse connection from the forearm - so i always try to keep the wrists flat and not turned sideways. or, for my hand to be at angles with my forearm. or for the wrists to be sticking up. to me, it's a tunnel of freedom - and you want the most impulses to travel the freest and fastest up and down the forearm.
this is probably completely off the subject - but whilst watching neeme jarvi conduct - i realized that at certain times he just dropped his hands to his sides and made sideways conducting motions as a tap dancer would. he even would shrug his shoulders to indicate the beat. i thought, 'very very cool.' with conducting, playing the piano, playing a sport - you have all these injuries you can get. but, if you find creative ways to move around freely - then they become less and less likely. i think that part of neemes conducting moves are to 'counter' some of his other 'repetitious' moves - and they are so creatively part of his conducting that they ARE conducting. even at one point, he moved his head sideways and just 'pretend' listened to the orchestra (for a couple of beats) to hear an 'answer' section - and at that point his entire body was relaxed. (and got a neck turn in). this complete freedom is exactly what is needed in piano technique, imo. very minimal but sometimes powerful impulses.