TL;DR: If you migrated system settings from a notebook Mac to a desktop, run
sudo pmset -a hibernatemode 0 autopoweroff 0 on the desktop machine.
In 2014, I replaced a MacBook Pro 17" with a refurbished late 2012 Mac Mini (Macmini6,2). One of these years I should probably ditch the home directory that I have been carrying around since Mac OS X debuted, but at the time, the MacBook was suffering from intermittent graphics card problems, and needed to be replaced ASAP. Playing musical chairs with the contents of my home directory really wasn't on the schedule.
Part of my thinking, actually, was that I really wanted the desktop to do the heavy lifting, and that I needed something smaller for on the road. So I would start with an empty home directory on the replacement portable.
The part I had not considered was that migrating the system settings from a laptop to a desktop would bring along some laptop-specific power settings. In particular, the Mac Mini started throwing all kinds of Sleep Wake Failure errors, and the system spontaneously rebooted after a few of these events. (I should have saved the logs, but I can't find them any more.) A bit of digging, and one of the Apple support forums recommended setting hibernatemode to 0 on a desktop Mac. It sounded absurd that this would have gotten changed, but sure enough, the migration to the Mini had brought along the value of 3 for hibernatemode. According to the documentation:
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.
No issues (knock on wood) since I changed back to the recommended default:
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.
Running OS X 10.9.5.