Rectangular sleeping bags are the initial and also most typical form you'll see on the market. I directly don't think there is much of a visible difference in between the fillings nonetheless synthetic fibers will certainly not soak up water and will certainly keep you warmer also if the bag is a little bit wet. A damp down resting bag is very hard to dry out as well as is taken into consideration even worse than having no sleeping bag at all.
Semi-Rectangular: I call this the cross. This backpacking bag is rectangle-shaped ahead and afterwards slenders along towards the feet. With this type, you obtain added space, but not as much weight as a true rectangular resting bag. For those who are claustrophobic, like me; we can reach sleep a little better inside a bag with added room in it and still have some benefit from the form.
One more item you could acquire is a sleeping bag liner. These offer extra heat on cold evenings, as well as can likewise be gotten rid of and washed, conserving your sleeping bag from the regular damage.