QSI vs ILMN vs PACB vs CDNA vs TMO

For growth investors, CareDx, Inc (CDNA) is the stronger pick with 13.

8% revenue growth year-over-year, versus -20. 3% for Quantum-Si incorporated (QSI). Illumina, Inc. (ILMN) offers the better valuation at 26. 0x trailing P/E (27. 2x forward), making it the more compelling value choice. Analysts rate Quantum-Si incorporated (QSI) a "Buy" — based on 2 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, Illumina, Inc.

(ILMN) is the cheapest at 26. 0x versus Thermo Fisher Scientific Inc. at 26. 2x. On forward P/E, Thermo Fisher Scientific Inc. is actually cheaper at 18. 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: Illumina, Inc. wins at 6. 43x versus Thermo Fisher Scientific Inc. 's 8. 86x.

Over the past 5 years, Thermo Fisher Scientific Inc.

(TMO) delivered a total return of +1. 9%, compared to -93. 9% for Pacific Biosciences of California, Inc. (PACB). Over 10 years, the gap is even starker: CDNA returned +393. 7% versus QSI's -90. 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), Thermo Fisher Scientific Inc.

(TMO) is the lower-risk stock at 1. 07β versus Quantum-Si incorporated's 3. 69β — meaning QSI is approximately 243% more volatile than TMO relative to the S&P 500. On balance sheet safety, Quantum-Si incorporated (QSI) carries a lower debt/equity ratio of 2% versus 142% for Pacific Biosciences of California, Inc. — giving it more financial flexibility in a downturn.

By revenue growth (latest reported year), CareDx, Inc (CDNA) is pulling ahead at 13.

8% versus -20. 3% for Quantum-Si incorporated (QSI). On earnings-per-share growth, the picture is similar: Illumina, Inc. grew EPS 170. 9% year-over-year, compared to -143. 0% for CareDx, Inc. Over a 3-year CAGR, PACB leads at 7. 6% 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.

Illumina, Inc.

(ILMN) is the more profitable company, earning 19. 6% net margin versus -41. 6% for Quantum-Si incorporated — meaning it keeps 19. 6% of every revenue dollar as bottom-line profit. Operating margin tells a similar story: ILMN leads at 19. 9% versus -39. 8% for QSI. At the gross margin level — before operating expenses — CDNA leads at 67. 0%, 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, Illumina, Inc. (ILMN) is the more undervalued stock at a PEG of 6. 43x versus Thermo Fisher Scientific Inc. 's 8. 86x. Both stocks trade at elevated growth-adjusted valuations, so expected growth needs to materialise. On forward earnings alone, Thermo Fisher Scientific Inc. (TMO) trades at 18. 7x forward P/E versus 27. 2x for Illumina, Inc. — 8. 5x cheaper on a one-year earnings basis. Analyst consensus price targets imply the most upside for TMO: 40. 8% to $654. 67.

In this comparison, TMO (0.

4% yield) pays a dividend. QSI, ILMN, PACB, CDNA do not pay a meaningful dividend and should not be held primarily for income.

For long-horizon retirement investors, Thermo Fisher Scientific Inc.

(TMO) is the stronger choice — it scores higher on the combination of lower volatility, dividend reliability, and long-term compounding (low volatility (β 1. 07), +222. 6% 10Y return). Quantum-Si incorporated (QSI) carries a higher beta of 3. 69 — meaning larger drawdowns in market downturns, which matters significantly when you cannot wait years for a recovery. Both have compounded well over 10 years (TMO: +222. 6%, QSI: -90. 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 Healthcare 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.