IMHO it's hard to beat hibernate in terms of overnight discharge (there isn't any to speak of and fewer things will automatically wake the SP from hibernate than sleep). However, going into and out of hibernate requires disk activity and resultant battery drain so if you hibernate frequently (not really my use case) it may actually be better overall to sleep. What I did was:
1. Set hibernate timers shorter than the sleep timers
2. Configured the cover to hibernate
3. Configured the power button to hibernate
4. Just to cover the bases I added hibernate to the power options
The downside of this is that the Windows logo never wakes up the machine, but that is not important to me
With this configuration it should never sleep before hibernate. I think that is the key, especially if you have a 8MB device (256GB and 512GB SP2s seem to be having the worst problems)