Hello this is my first post I'm a very young backpacker and need some help picking out some gear. OK first things first the temperature I'm going to be sleeping in is about 30 to 45 degrees. I need a new sleeping bag and I want it light and cheap so I'm thinking synthetic. So I was thinking that the 20 degree bag would be the obsessive choice as it will be lighter but I weigh about 95 pounds and am a very cold sleeper. So should I get the 0 degree bag to keep warmer??? Here are the two bags I'm looking at now but feel free to recommend other bags mt budget would be about 150$ and my max weight would be 4 pounds for 0 3 pounds for +20.

http://www.amazon.com/gp/product/B0068BE...;pf_rd_i=507846
OR
http://www.amazon.com/Slumberjack-Degree...erjack+lonepine

Thanks for any help!