WSUS for SQL server patching
You'll often want a lot more control over that than WSUS offers. For example, you may have certain servers that you want to patch during maintenance windows. You may also want to be very careful about how you patch clusters, servers participating in log shipping, mirroring, replication, etc.

While they certainly exist, I don't personally know of any shop that uses WSUS to patch SQL Server. That doesn't mean it's not a good idea, but combining the variables above with the fact that there are only so many public updates to SQL Server that propagate to Windows Update in any given year, I just don't know how much you'll really gain by trusting it to do its thing.