When investing in index funds, the most important thing to consider is the expense ratio because similar index funds from different companies invest in the same stocks, so the difference in the return on your investment will only be affected by the management fees which each respective fund charges. Take a look at Fidelity Spartan Index Funds, which have the lowest expense ratio in the industry (0.10%). The Fidelity's equivalent to Vanguard's VTSMX is Spartan Total Market Index Fund (FSTMX). Its only downside is that it requires a minimum initial deposit of $10K, compared to $3K at Vanguard.
Here is an interesting article that talks about a research study about investing in index mutual funds and the lack of understanding that a lot of investors have regarding the fees
http://knowledge.wharton.upenn.edu/a...KEN=80 152872