>>1718137Hej OP,
first thing I would do is check what night temperatures you can expect in your area, during the seasons you intend to go /out/.
"Why this autism", you might ask. Well, knowing what you're up against will let you choose the best solution. I personally was taken by surprise where I live, because in the mountains temperatures dropped below freezing in the mountains at night.
Once you know the warmest and coldest temperatures you might run into, you can choose a solution.
Don't forget that if it's cold, a high R-value sleeping pad will protect you. The bottom of a sleeping bag does NOTHING to protect you from the cold.
I'd go with a sleeping bag + a liner, like others have said. I'd recommend the strategy to have a bag which is a bit too cold, then boost its capacity when needed.
In summer, take out the liner. In colder seasons, put it in. Don't forget there are other tricks as well: put your jacket on top of your sleeping bag as 3rd blanket, empty out your backpack and put the feet end inside, wear gloves, socks and a beanie cap.
Down bags stow much more compact than synthetics, but cost more. I have a mid range down bag rated between -2°C and 15°C - this is exactly my temperature range in summer to fall. It's small, but cost me about 200 EUR.
Lycka till!
