The other sacrifice is the size or thickness of the bag. A mummy sleeping bag essentially will certainly be much smaller sized for bring around which is why it is a preference for many backpackers/hikers. The rectangular resting bag isn't as small yet because it's not common to be lugging it, apart from somewhere in a vehicle while getting to your intended location, the bulkiness of the bag is not as large a problem.
Remember that with time, from typical use, a treking sleeping bag will certainly lose its warming performance. This results from the fill obtaining a bit much more compressed. This will cause the "air pockets" to go away.
The shape of the real resting bag is to personal preference. The general selections are the normal rectangular form, the conical form, or the mommy bag. Some individuals might not such as the feel of sleeping in a regular rectangular shaped bag, favoring the closeness of a tapered one, whereas others may really feel too claustrophobic.