I'm using a Sharepoint list to keep track of items that users have favorited, mapping user aliases to item IDs. I have two options, and I'm wondering which is more efficient. One makes for less total items in the list, but the other takes less processing per operation- I'm wondering if either of these considerations are negligible in terms of SharePoint.
Create a new item with one user alias and one ID number every time an item is favorited, removing it when un-favorited.
Check if an item with the user's alias exists. If it does not, create a new item with the alias and the item's ID. If it does, append the item ID after the previous IDs associated with the user's alias. When removing a favorite, that particular ID needs to be located in the list of IDs and removed.