What is the difference between pmset and systemsetup sleep options?

In this case, systemsetup is a high level wrapper that is analogous to the System Preferences UI. Both call the lower level power API which are the internals about how the system actually stores these values for the hardware to use and implement. pmset is a lower level tool that reads the API/hardware values directly, so I would generally trust that over the higher level tools like Energy Saver or system setup

If you are right and there is a discrepancy, you might have to file a bug report with Apple to figure out if it's really a bug or just that the information is being mixed up before it is presented to you.

You can go directly to the source file as it's stored at /Library/Preferences/SystemConfiguration/com.apple.PowerManagement.plist and perhaps it can break the tie between which of these three tools is telling you the correct information?

In all my computers, the numbers match up, so perhaps the systemsleep values are incorrect for your hardware or OS build?

After doing some more testing, it seems the results from systemsetup -getsleep correlate with the Power Adapter settings on the Energy Adapter prefpane. When I use -setsleep 10, the Display Sleep timer also jumps to 10 minutes, and vice versa.

Also, when I check Prevent computer from sleeping when display is off, systemsetup -getsleep returns Sleep: Computer sleeps Never, while unchecking Put hard disks to sleep when possible causes Sleep: Disk sleeps Never.

In conclusion, it would seem the reason for the deviating values of pmset and systemsetup is that I was testing while on battery power, so pmset returned battery values, while systemsetup always returns power adapter values.

My MacBook Air is an Early 2015 model and installed with macOS 10.14.2, and I've encounter the similar issue.

It puzzled me at first, but after poking-around for a while, I found:

1. pmset is able to set different sleep configuration for battery mode and AC mode, with -b and -c options respectively. What info pmset -g displays depends on whether the your MAC is using battery or AC power. So, if you want to know the complete settings pmset currently holds, you should run pmset -g twice, with and without power adapter plugged on respectively.

2. systemsetup has no options to distinguish battery and AC power setting.

3. If you use systemsetup to change the power settings, the settings in GUI System Preference==>Energy Saver==>Power Adapter changes accordingly, and vice versa. But, the settings in System Preference==>Energy Saver==>Battery always stay the same after using systemsetup. So, it is obvious that systemsetup can only modify AC-mode power settings.