XLU, a hugely popular fund, only invests in utilities companies that are included in the S&P 500. This is both an advantage and a weakness. The fund dominates its segment, with huge assets and volume, but it's also more concentrated in a handful of large firms. Competing utilities ETFs offer broader exposure to the full market-cap spectrum, meaning XLU is not the best Fit to our neutral utilities sector benchmark. Still, XLU is a solid choice for exposure to the segment.