I have the FL and the Kifaru. They really don't overlap in purpose all that much so which cost you should get it completely up to your hunting style. For active hunting you should get either the Cirrus or Uncompaghre, which one should depend more on temps you expect to be in and your preference on hood or not. The Kifaru is a sleeping bag that you wear. It will only be used in the coldest of conditions when either glassing, still hunting or hiking downhill only.
As far as sizing, it's all over the board. I wear an XL-T t-shirt most of the time and wear a L Uncompaghre, XL Cirrus (although I sold it because it was too short yet bulky in the gut) and a XXL Lost Park Parka (which fits perfect in the chest and in length, a little bulky in the gut but not bad).