I'm a big guy (over 6' and about 250) and I hate mummy bags, I like to move around IN a bag and not have the bag stick to me. I went to Cabelas and looked at bags. They had 30 or 40 hanging up on hangers. I tried a bunch of rectangular bags by putting them on the floor and actually getting in them. I look for large zippers, duck cloth outside and flannel lining. I bought 2 bags....same mfgr & model. One rated to 20 degrees and one rated to -20. Both bags together cost me less than $450. That was 5 years ago and still using them, love them both as they are extra wide and extra long.
Neither one are back packing sleeping bags as I don't back pack anymore as I am too damn old.
Last November deer hunting here in Colorado, the temp at night got down to 5 degrees and I was warm as toast in the -20 bag.