The bag on the left is my main bag, a Mountain Hardwear Flip 25/40. Considered a hybrid bag as it is a mix of a rectangular and mummy bag, it is extremely versatile. Normally I hammock camp and therefore have a thin base layer under me. The two sides have different temperature ratings which allows me to use the appropriate side for the situation. In very cold temperatures I use an additional layer between the hammock and the bag and put the warmer side facing the top. The fill is burly and provides a good layer of padding against rough ground if there is no place to pitch the hammock. It also opens all the way up if you want to use it as a blanket or zip it into another bag. Dual zippers are a nice feature if your feet get hot or you need to get or keep an arm out.
Selecting the right bag depends on your needs. What type of camping will you be doing? Do you have to have a mummy bag? What features are must haves and which are just extras? The zippered external pocket on my bag is nice but was not essential for me. I would have bought the bag even if it didn't have it. Shopping around and looking for sales at outdoor stores can save you some serious cash. I looked at this bag at one store and was going to pick it up. I decided to check another local store the following weekend and caught the bag at 50% off.
If space is not a concern a carrying strap like the one above is handy to keep you bag closed and provides an easy solution for transport. After time on the road I always let any bag that I take dry in the open for at least 24 hours. I store the good bag open under the bed. You should not store a poly-fill bag in a stuff sack as it will compress the insulation and considerably cut the fill's warmpth. This is not as much of a concern with the older flannel bag, we keep it rolled up but not ratcheted down. I split the difference on the cheap mummy bag: I store it in the bag but not compressed.