<prompt> Human: This summer Fidelity slashed expense ratios on many of their mutual funds. In many cases including the SP 500 index fund, where FUSVX now offers 0.045 expense ratio vs Vanguards VFIAX at 0.05, Fidelity now offers cheaper solutions that Vanguard.And in my opinion, Fidelity also offers more user-friendly and feature-filled mobile and web applications. Not sure about customer service.Are they the new king of index fund investments, or is this just a short-term promotion? Will Vanguard respond with even lower expense ratios?  <response>: Huh, Ive got a good chunk of change invested in FUSVX. I didnt know the ER was going down a half basis point. Interesting.That said, were talking about a difference of 50 cents per 10k invested. I doubt it makes a ton of difference. I never considered vanguard the old king, and I wouldnt crown fidelity the new king. They both have some good fund offerings. FUSVX was already rated as as 5 star gold fund by morningstar even before this fee drop. 