I think you need to start by deciding on your overall desired asset allocation. Your target funds most likely have a mix of US stocks, international stocks and bonds. The Large Cap Index Fund is limited to S&P 500 stocks. Do you have any other accounts in addition to the 401k? What is your desired overall asset allocation? Do you want 100% stocks, a certain ratio of stocks and bonds? some international exposure?
Once you decide on your overall allocation, then you need to look at the totality of your accounts and figure out what options you have for achieving that allocation and what the expense ratio is for each option. Then you decide on the most optimal way of achieving that allocation (cost, ease of maintaining the desired ratio, ease of rebalancing, tax efficiency, etc.)