Eggsnham, I'm getting awfully tired counting the enchantingly peeling sheep!
It is an interesting question though, and for that, I'll give my response with a hint of silly comprehensively thorough matter sprinkled on the top.
Once I begin to think of the most comfortable sleeping place, it's nearly impossible to not take in count the context of those places and times that come first in to mind.
Was it the hotel bed after a 100h work week and a 19h physically very demanding work day, even though I only had time to sleep for a couple of hours, before having to sign out and begin the journey back home?
Was it the bed after a rough two-week manouever in freezing Lapland in the deepest winter during military service, when I slept for 20 hours straight on a moving train. On a very thin foamy "matress", cocooned in a sleeping bag, quite sleep deprived being an understatement?
Was it the bed, when I shut my eyes in my then-girlfriend's slightly-too-small-for-both-of-us bed, trying to keep my portion of the blanket, when we were the most madly in love with each other?
Those beds felt extravagant to say the least, even though they wouldn't seem like such more objectively. Now they might even be uncomfortable or awful, but they're the first that came to mind.
On another note, it is truly strange how little attention we often give, how little investments we usually make, for the places we spend about a third of our lives in, and a proper sleep and rest being such a huge factor in the quality of our daily lives.