shorter skis will actually be harder to turn as you will be in the snow more....and will be less stable.
for your size and weight....
out right powder day or days after powder day if your tree do not get skied much. fatter/longer skis will float easier and more speed and there for be quicker and more nimble with more speed range than smaller skis. Reverse camber and sidecut add to the nimblness of the ski
193 Nordica Radict(if you can find it)
189 K2 Pontoon 2
196(or 186) on3p pillowfight
186 Volkl 2
196(or 187) Praxis Protest
basically anything big than you think you need for snow that will never find bottom on. do realize a ski like the On3p Pillowfight is going to get off the bottom in even 6 inches of snow faster than a smaller ski.
powder skis with some all mountain ability these skis will almost have the float of the above with some better ability on harder/packed snow
193 volkl shiro as mentioned already
188 Rossi Super 7
191(or 186) On3p billy Goat
193 Nordica Helldorado or Patron
basically my theory is western trees are open, and unless you sliding sidewyas though them longer/fatter skis are more nimble than short/sknnier skis.