Do MacBooks have a true "Hibernate" option?
When newer laptops are put to sleep, they should save the contents of the RAM to /var/vm/sleepimage but keep the RAM powered as well. Desktop Macs should just use normal sleep mode by default.

man pmset:

hibernatemode = 0 (binary 0000) by default on supported desktops. The
system will not back memory up to persistent storage. The system must
wake from the contents of memory; the system will lose context on power
loss. This is, historically, plain old sleep.

hibernatemode = 3 (binary 0011) by default on supported portables. The
system will store a copy of memory to persistent storage (the disk), and
will power memory during sleep. The system will wake from memory, unless
a power loss forces it to restore from disk image.

hibernatemode = 25 (binary 0001 1001) is only settable via pmset. The
system will store a copy of memory to persistent storage (the disk), and
will remove power to memory. The system will restore from disk image. If
you want "hibernation" - slower sleeps, slower wakes, and better battery
life, you should use this setting.



0 (traditional sleep mode): fast wake up and sleep, saves disk space
3 (default safe sleep mode): fast wake up and sleep, state is kept when losing power
25 (hibernation): saves energy, state is kept when losing power


You can see which mode your Mac uses with pmset -g | grep hibernatemode and change it with sudo pmset -a hibernatemode $mode.

Some newer Macs support a standby mode on 10.8 and later. Even if hibernatemode was set to 3, they power off memory after a bit over an hour of sleep.