Richard has several platforms with different OSs, and he's having issues with maintaining contacts. He gets a lot of duplicates. Leo says that synchronization is a hard, universal problem. It guards against deleting anything, just in case. So you end up with duplicates. Leo uses Google Contacts. But even that doesn't solve the duplicates issue. But the sync is quite good. One solution that Leo recommends, that's iPhone only, is Sunshine. It can dedupe, as well as sync. It's invitation-only right now, but they are working hard at trying to crack this nut. Full Contract is another.