well Xbox syncs with PC
It was terrible, at least in the 360 era.
It worked apparently if you started with an xbox live account and wanted to move to PC as well. If you started with a games for windows live account and wanted to go to xbox, no joy - you had to create a second account.
So thats how I ended up with two separate microsoft accounts, borne out of what was originally a gfwl account and an xbox account.
How I Learned To Stop Worrying And Love The Subscription