After reading the article about the sleeping theories I think that the theory I agree the most with, is the one proposed by Crick and Mitchison.
Considering the dreaming process as a "reverse learning" makes an actual sense to me. Also other experts say that dreams are a mixture of external stimuli, distant memories and recent experiences, and while our body rest the brain process all that information and tries to put some order in the chaos of our subconscious.
From my point of view, this theory is actually ascertainable if I think of those dreams that I had had (at least the ones that I can remember). Most of the time, they were a combination between my memories and recent events or thing that I had been thinking about.