can I control whether the iphone overrides the mac or vice versa when syncing

First, your mac will not be able to sync with iCloud if your aren't running OS X Lion (10.7.2 or later). Also, you don't want to be syncing your contacts with both iCloud and iTunes or you will end up with duplicates. Choose one and disable the other.

What I do is turn off iCloud contact syncing and get all your contacts to match first, then turn iCloud contact syncing back on. To do this, follow these steps:

1. Turn off iCloud syncing on your devices by going to Settings>iCloud and turning Contact to Off. When prompted choose to keep your data on your device. (If you are running OS X Lion and are syncing contacts on your mac with iCloud you will want to go to System Preferences and uncheck contacts syncing there as well.)
2. Download and use the app My Contacts Backup. If your phone contacts are the ones you want to transfer to your other devices, use the app on your phone to back up your contacts as an attachment to an email. Send this email to yourself.
3. Delete the contacts on your iPad by tapping the settings (gear shaped) icon at the bottom right of My Contacts Backup. In the window that opens, scroll to the bottom and tap Remover All Contacts. Next, open the email you sent earlier on your iPad and tap the attachment to import the contacts from your phone. Your iPad contacts should now match the contacts on your phone.
4. On you mac, open Address Book, tap a single contact, press Command-A to select all contacts, go to File>Export>Export vCard, save this file on your desktop. This is just a precautionary backup that can be used to restore your contacts if anything goes wrong. Now select all contacts in Address Book as before and press your Delete key to remove them. Next, open the My Contacts Backup email on your mac and double-click the attachment to import the contacts from your phone to Address Book. Now your Address Book contacts should match the contacts on your phone as well.
5. Go to iCloud.com, sign into your account and open your contacts. If your contacts are still there, click on a single contact, press Command-A to select all contacts, press the Delete key to remove them.
6. Now turn on iCloud contact syncing on your devices again; if prompted choose merge. As all your contacts now match you shouldn't have any issues with which one takes precedence in uploading to iCloud.

You're welcome.