ETF World vs S&P 500: Which to Choose?

Comparing a world fund with an S&P 500 fund means comparing two perimeters, not two qualities of management. The MSCI World gathers about fifteen hundred companies from twenty-three developed countries, the S&P 500 five hundred American companies selected by a committee. Because weighting follows market capitalisation, the United States already accounts for close to seventy per cent of the world index: the two baskets overlap heavily, and their twenty largest lines are essentially the same companies. The performance gap between them over ten years is therefore explained less by diversification than by the relative weight of the thirty per cent that is not American, and by the dollar against the euro, which acts on both without appearing in either index. The useful question is therefore not which returned more, but which perimeter you want to hold for the twenty years ahead, since that is the only part of the decision you control.

The eternal debate

The choice between a World (MSCI World) ETF and an S&P 500 ETF is perhaps the most common dilemma facing passive investors. Both are excellent core portfolio holdings, but they serve different purposes and carry different risk profiles.

What each index covers

The MSCI World Index tracks approximately 1,500 large and mid-cap stocks across 23 developed markets. The US represents about 70% of the index, with Japan (~6%), UK (~4%), and other developed markets making up the rest.

The S&P 500 Index tracks the 500 largest US companies by market capitalization. It represents approximately 80% of the total US stock market value.

Historical performance comparison

Over the past 10 years (2016-2026), the S&P 500 has outperformed the MSCI World by approximately 2-3% annually. This outperformance is largely driven by the dominance of US tech giants (Apple, Microsoft, Nvidia, Amazon, Google, Meta, Tesla).

However, this hasn't always been the case. During 2000-2010, international stocks outperformed US stocks, and the MSCI World's diversification provided better risk-adjusted returns.

Diversification analysis

The S&P 500 concentrates 100% in the US market. While the US is the world's largest and most innovative economy, geographic concentration creates specific risks: regulatory changes, dollar depreciation, or sector-specific downturns can disproportionately affect returns.

The MSCI World spreads risk across 23 countries. When US markets underperform, other regions can partially offset losses. This is the fundamental value of diversification.

Cost comparison

Both index categories offer very low-cost ETFs:

• S&P 500: TER as low as 0.03% (Vanguard VOO) to 0.15% (European UCITS ETFs)
• MSCI World: TER typically 0.12% to 0.38% depending on provider and PEA eligibility

The S&P 500 generally wins on cost, but the difference is minimal.

Our verdict

For investors building a single-ETF portfolio, MSCI World provides better diversification with still-strong exposure to the US (70%). For those willing to manage a 2-3 ETF portfolio, combining S&P 500 with European and emerging market ETFs can achieve similar diversification at a lower overall TER. Neither choice is wrong, the key is consistency and long-term commitment.

What the remaining thirty per cent changes

The non-American part of the MSCI World, Japan, the United Kingdom, the euro area, Switzerland, Canada, Australia, does not change the nature of the portfolio but its sector balance. It reduces the weight of technology, raises that of banks, industrials and healthcare, and slightly lowers concentration in the ten largest lines. Through a decade of American dominance that part cost performance; through earlier decades it had added some. Nobody knows which of the two configurations comes next, and that is exactly the argument for the wider perimeter: it does not ask you to forecast.

Currency, absent from both indices

An investor in euro holding either carries substantial currency risk, since most of the underlying earnings are denominated in dollars. The index itself is computed in its reference currency and says nothing about that risk. A ten per cent fall in the dollar therefore removes roughly ten per cent of the euro return of an S&P 500 fund, and slightly less of a world fund, part of whose assets are already in euro, yen or Swiss franc. Currency-hedged versions exist, but their cost, equal to the interest rate differential between the two currencies, can exceed a point a year, and they make far more sense over a short horizon than over twenty years.

Holding both, a false good idea

Adding an S&P 500 fund to a world fund means overweighting the United States without deciding to: the portfolio moves from seventy to eighty or eighty-five per cent American exposure depending on the weights, with two lines, two orders and two sets of dealing charges instead of one. If the overweight is wanted, it is achieved more simply by holding the American fund directly. If it is not, it is an accident of construction, and that is precisely what measuring a portfolio's overlap is meant to reveal.

Which one for which horizon

Neither index is more prudent than the other in any meaningful sense: both are equity, both can fall by half. What differs is where the concentration sits. The S&P 500 concentrates on one country and, today, on around ten companies that make up a third of it. The world index spreads that across twenty-three countries while keeping most of the same companies at the top. Over a horizon of twenty years, the wider perimeter asks for no forecast about which country leads next, and that is its whole argument.