[pct-l] Sleeping Bags: 15 vs 20 degree and down treated bags

[Tracy Fisher]

I am in the process of choosing between several sleeping bags from several different makers (not a quilt) but am now so overwhelmed with all of the sales chatter that I decided to get some advice from you all to perhaps help me in making my final decision. 

   1. Is it better to get a warmer 15 degree bag that will keep you comfortable in the colder places on the PCT, or a cooler 20 degree bag that keeps you comfortable in the warmer places, and just add more clothes in the colder places?

  2.  Has anyone had experience with down bags where the down filling has been treated with the new water repellant technology?  Each company has its own name for it, for example, Mountain Hardwear calls it Q Shield.  It seems like more and more companies are using this product.