Putting it down so that I can go back to my 3x3, to be honest. I don't really enjoy big cubes all too much, though I do them once in a while.
My favourite phase in Reduction is either edge pairing (though I suck at it) or the 3x3 phase (Rouxduction FTW!).
My favourite phase in K4(+)... Anything but ELL. I seriously hate ELL and I suck at it, hence I don't use K4... Though, I must admit, if I ever bother to practice big cubes a bit more hardcore, and better my ELL comms, then I'd probably switch.