I really have one real demand. The left stick should be in the upper position.
Let's just say I don't game on the PlayStation because I like the controller, I game on it despite of that thing. All of Nintendo's controllers got that part right (with the exception of the Classic Pro controller, but that was made primarily for 'D-Pad-games' anyway). Your thumb is naturally in the upper position and so should the left stick otherwise it's uncomfortable and unnatural.
That said I don't mind the position of the right stick as much, probably because you use that thumb for several different actions (the stick as well as the face buttons). I'm fine with it being symmetrical, but I think I still prefer an asymmetrical placement. In most games I play, I use the face buttons more often than the right stick, so with the stick down my hands will remain symmetrical. N64, GameCube and XBox got that part right. Never owned a Microsoft console myself, but I've used the original XBox's controller enough to know. The WiiU sadly fails in that part, but luckily the GamePad is big enough to position my right hand differently so it remains comfortable enough.
So long story short, I think I prefer asymmetrical, with the left one in the upper position naturally.