MMC vs AON

For growth investors, Aon plc (AON) is the stronger pick with 9.

4% revenue growth year-over-year, versus 7. 6% for Marsh & McLennan Companies, Inc. (MMC). Aon plc (AON) offers the better valuation at 18. 4x trailing P/E (16. 5x forward), making it the more compelling value choice. Analysts rate Aon plc (AON) a "Buy" — based on 38 analyst ratings — the highest consensus in this comparison. The "better buy" depends entirely on your goals: growth investors should weight revenue trajectory, value investors should weight P/E and PEG, and income investors should weight dividend yield and streak.

On trailing P/E, Aon plc (AON) is the cheapest at 18.

4x versus Marsh & McLennan Companies, Inc. at 21. 3x. On forward P/E, Aon plc is actually cheaper at 16. 5x. The PEG ratio (P/E divided by earnings growth rate) is the most growth-adjusted single valuation metric: Marsh & McLennan Companies, Inc. wins at 0. 88x versus Aon plc's 1. 10x — a PEG below 1. 0 traditionally signals the market is underpricing earnings growth.

Over the past 5 years, Marsh & McLennan Companies, Inc.

(MMC) delivered a total return of +36. 5%, compared to +26. 2% for Aon plc (AON). Over 10 years, the gap is even starker: AON returned +219. 8% versus MMC's +209. 8%. Past returns do not guarantee future results, and the stock with the higher historical return may already have its best growth priced in.

By beta (market sensitivity over 5 years), Aon plc (AON) is the lower-risk stock at 0.

10β versus Marsh & McLennan Companies, Inc. 's 0. 14β — meaning MMC is approximately 43% more volatile than AON relative to the S&P 500. On balance sheet safety, Marsh & McLennan Companies, Inc. (MMC) carries a lower debt/equity ratio of 162% versus 173% for Aon plc — giving it more financial flexibility in a downturn.

By revenue growth (latest reported year), Aon plc (AON) is pulling ahead at 9.

4% versus 7. 6% for Marsh & McLennan Companies, Inc. (MMC). On earnings-per-share growth, the picture is similar: Aon plc grew EPS 36. 3% year-over-year, compared to 8. 6% for Marsh & McLennan Companies, Inc.. Over a 3-year CAGR, AON leads at 11. 2% annualised revenue growth. Higher growth typically commands a higher valuation multiple — check whether the premium P/E or P/S is justified by the growth rate using the PEG ratio.

Aon plc (AON) is the more profitable company, earning 21.

5% net margin versus 16. 6% for Marsh & McLennan Companies, Inc. — meaning it keeps 21. 5% of every revenue dollar as bottom-line profit. Operating margin tells a similar story: AON leads at 25. 3% versus 23. 8% for MMC. At the gross margin level — before operating expenses — AON leads at 47. 7%, reflecting greater pricing power or product mix advantage. Stronger margins indicate durable pricing power, lower cost of revenue, or higher mix of software/services. They are one of the clearest signs of business quality.

The PEG ratio (forward P/E divided by expected earnings growth rate) is the most precise measure of undervaluation relative to growth potential.

By this metric, Marsh & McLennan Companies, Inc. (MMC) is the more undervalued stock at a PEG of 0. 88x versus Aon plc's 1. 10x. A PEG below 1. 0 is traditionally considered the threshold for growth-adjusted undervaluation. On forward earnings alone, Aon plc (AON) trades at 16. 5x forward P/E versus 16. 9x for Marsh & McLennan Companies, Inc. — 0. 4x cheaper on a one-year earnings basis. Analyst consensus price targets imply the most upside for AON: 29. 0% to $404. 40.

All stocks in this comparison pay dividends.

Marsh & McLennan Companies, Inc. (MMC) offers the highest yield at 1. 8%, versus 0. 9% for Aon plc (AON).

For long-horizon retirement investors, Aon plc (AON) is the stronger choice — it scores higher on the combination of lower volatility, dividend reliability, and long-term compounding (low volatility (β 0.

10), 0. 9% yield, +219. 8% 10Y return). Both have compounded well over 10 years (AON: +219. 8%, MMC: +209. 8%), confirming both are viable long-term holds — but the lower-volatility option typically results in less emotional selling during corrections. Retirement portfolios generally favour predictability over maximum returns. Consult a financial advisor before making allocation decisions.

Both stocks operate in the Financial Services sector, making this a peer-level intra-sector comparison — the same macro tailwinds and headwinds will affect both.

These fundamental differences mean investors should not choose between them on a single metric — the "better stock" depends entirely on which of these characteristics aligns with your investment strategy.