Selecting sleep under the Apple menu triggers the settings you have in Energy Saver Preferences. In other words, it activates sleep immediately when selected.
I don't think there is a recommended preference setting - here are mine:
Computer sleep: 1 hour
Display sleep: 10 mins
Put hard disks to sleep when possible - selected
Wake for network access - selected
Allow power button to put the computer sleep - selected
Start up automatically after a power failure - not selected.
However, if you asked ten different users what their settings are you would probably get eleven different answers .
I recently discovered that there is a physical difference between the 2 sleep modes with my late 2009, 21.5" imac running OS X 10.8.2. It stays warm when in sleep triggered by energy saver but cools right down to ambient temperature when put to sleep from the sleep command in the apple menu.
Any ideas why this should be?
There are 2 sleep modes. One is when the power saver time is past. The HD is shut down and video is turned off, and the CPU slows down, but CPU and RAM are left running for an instant restart.
Then there is deep sleep initated by the user either from the Apple Menu or by hitting command-option-eject on the keyboard. In this case, RAM and all system caches are saved to disk, and then the Mac is powered down, leaving only the Power Management Unit alive. This is almost like Shut Down, except when awakened the state of RAM etc. is reloaded from disk instead of doing a system boot. Waking is pretty fast, but slower than light sleep.
If a laptop on battery power is left long enough, it will go from sleep to deep sleep to save battery. You'll notice it takes longer to enter deep sleep because of writing everything to disk.