Replying to Coat and pants for powder, and info about puffy/down jackets please

Alright so I'll be skiing a fair amount of powder this season.  Should I look for certain things when I buy gear that will be used mostly in powder.  I was thinking about getting some of the 08 Oakley that is 10k/10k.  That should be good right?  Or should i go higher? 
Also I usually wear my pants XXL and my coat L jacket, would it be detrimental to buy gear that baggy (I'm 5'10 145 lbs.) if I'm using it mostly for pow, would it get int he way or would I probably be good?

Also for peeps that wear puffy/down jackets do they get int he way at all when you ride park or anything cause some of them are pretty heavy/beefy. 

also would a puffy/down jacket be as good in terms of water proofness and breathability?
and finally, would a puffy be a good idea for powder skiing?