Look closely at the two links in the OP.
With today's interest rates, you can get 0.01% in one or 0.01% in the other.
For those in the "picture worth 1000 words" camp, see the "Hypothetical growth of $10,000" charts for both over the past 4-5 years.
Until the interest rate environment changes drastically...it doesn't matter. Ours happens to be VMMXX, with a current balance of $0.05.