sync × 14
synchronization × 2
One question actually has both tags.
I think "sync" is used more because, well, it's a simple abbreviation and the full word is hard to spell. Also, a lot of devices have used "Sync" as their official term for what they're doing with your data. (I know that all those years I used a Palm device I don't know that I ever saw the word "synchronization" in any documentation.)
The grammarian in me prefers spelling the word out, but I'll go with the community's preference.