GSK vs MRK vs AZN vs PFE

For growth investors, AstraZeneca PLC (AZN) is the stronger pick with 8.

6% revenue growth year-over-year, versus -1. 6% for Pfizer Inc. (PFE). GSK plc (GSK) offers the better valuation at 6. 7x trailing P/E (10. 4x forward), making it the more compelling value choice. Analysts rate Merck & Co. , Inc. (MRK) a "Buy" — based on 37 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, GSK plc (GSK) is the cheapest at 6.

7x versus AstraZeneca PLC at 28. 0x. On forward P/E, Pfizer Inc. is actually cheaper at 8. 7x — notably different from the trailing picture, reflecting expected earnings growth. The PEG ratio (P/E divided by earnings growth rate) is the most growth-adjusted single valuation metric: GSK plc wins at 0. 73x versus Merck & Co. , Inc. 's 1. 02x — a PEG below 1. 0 traditionally signals the market is underpricing earnings growth.

Over the past 5 years, AstraZeneca PLC (AZN) delivered a total return of +84.

2%, compared to -14. 8% for Pfizer Inc. (PFE). Over 10 years, the gap is even starker: AZN returned +269. 2% versus PFE's +28. 5%. 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), GSK plc (GSK) is the lower-risk stock at 0.

44β versus AstraZeneca PLC's 0. 63β — meaning AZN is approximately 43% more volatile than GSK relative to the S&P 500. On balance sheet safety, AstraZeneca PLC (AZN) carries a lower debt/equity ratio of 61% versus 111% for GSK plc — giving it more financial flexibility in a downturn.

By revenue growth (latest reported year), AstraZeneca PLC (AZN) is pulling ahead at 8.

6% versus -1. 6% for Pfizer Inc. (PFE). On earnings-per-share growth, the picture is similar: GSK plc grew EPS 348. 4% year-over-year, compared to -3. 5% for Pfizer Inc.. Over a 3-year CAGR, AZN leads at 9. 8% 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.

Merck & Co.

, Inc. (MRK) is the more profitable company, earning 28. 1% net margin versus 12. 4% for Pfizer Inc. — meaning it keeps 28. 1% of every revenue dollar as bottom-line profit. Operating margin tells a similar story: MRK leads at 36. 2% versus 23. 4% for AZN. At the gross margin level — before operating expenses — AZN leads at 81. 9%, 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, GSK plc (GSK) is the more undervalued stock at a PEG of 0. 73x versus Merck & Co. , Inc. 's 1. 02x. A PEG below 1. 0 is traditionally considered the threshold for growth-adjusted undervaluation. On forward earnings alone, Pfizer Inc. (PFE) trades at 8. 7x forward P/E versus 21. 7x for Merck & Co. , Inc. — 13. 0x cheaper on a one-year earnings basis. Analyst consensus price targets imply the most upside for MRK: 16. 1% to $129. 31.

All stocks in this comparison pay dividends.

Pfizer Inc. (PFE) offers the highest yield at 6. 7%, versus 1. 8% for AstraZeneca PLC (AZN).

For long-horizon retirement investors, Merck & Co.

, Inc. (MRK) is the stronger choice — it scores higher on the combination of lower volatility, dividend reliability, and long-term compounding (low volatility (β 0. 45), 2. 9% yield, +164. 7% 10Y return). Both have compounded well over 10 years (MRK: +164. 7%, PFE: +28. 5%), 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 Healthcare sector, making this a peer-level intra-sector comparison — the same macro tailwinds and headwinds will affect both.

In terms of investment character: GSK is a mid-cap deep-value stock; MRK is a large-cap deep-value stock; AZN is a large-cap quality compounder stock; PFE is a mid-cap income-oriented stock. 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.