Many people have asked me why they should purchase a canvas swag rather than a light weight nylon bivy. My answer is always 'They are two very different products, and it depends on what you are planning to use them for'.
I'll outline below the differences in Nylon and Canvas in the hope that it will clarify what you are after.
Canvas is made from a heavy weave cotton, making it stronger and more durable than nylon but in turn, weigh more.
Canvas swags are difficult to damage. If it is somehow ripped, this rip won't grow and become a gapping hole. It is easily mended with a patch or sewn up. Nylon is difficult to mend and often the smallest tear or burn hole from a spark becomes a large window in no time at all.
Cotton breathes a lot better than nylon, which reduces the condensation that gathers inside.
Cotton canvas is cooler in the heat and warmer in the cold weather. In the sun, Nylon warms up quickly causing you to cook inside and cools as soon as the sun disappears.
Cotton is a renewable material that is biodegradable.
If weight and space isn't an issue the canvas swag is definitely your best bet. In saying that, if you need to save on space, removing the comfortable foam mattress and replacing it with an air mattress will decrease the bulk of the swag and weight significantly.
Swags are not ideal for tramping or taking on a bicycle. They have been used for hunting, fishing, camping, taking to parties, heading 'out back' for the weekend, on motorbike, jet boat and helicopter excursions. Many fishermen/women, hunters and campers have hiked small distance with them, eg. up a river to stay the night, but they are mainly used when there is a vehicle to carry them.