I got the "choices" concept based upon information as follows from Apple documentation.
"Reset Sync History
If you find that some of your data syncs to your device but you see an unexpected number of changes or modifications, you may need to reset your sync history. This causes iTunes to prompt to Merge or Replace information on the device when you next attempt to sync your information. To reset your Sync History:
Open iTunes.
From the Edit menu, choose Preferences.
Click the Devices tab.
Click the Reset Sync History button."
If it merges by default, then perhaps I have a different problem. Still seeking advice. Thanks.