XGN vs CSTL

For growth investors, Exagen Inc.

(XGN) is the stronger pick with 19. 7% revenue growth year-over-year, versus 3. 7% for Castle Biosciences, Inc. (CSTL). Analysts rate Castle Biosciences, Inc. (CSTL) a "Buy" — based on 11 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.

Over the past 5 years, Castle Biosciences, Inc.

(CSTL) delivered a total return of -68. 1%, compared to -80. 8% for Exagen Inc. (XGN). Over 10 years, the gap is even starker: CSTL returned -10. 1% versus XGN's -84. 2%. 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), Castle Biosciences, Inc.

(CSTL) is the lower-risk stock at 0. 88β versus Exagen Inc. 's 1. 37β — meaning XGN is approximately 55% more volatile than CSTL relative to the S&P 500. On balance sheet safety, Castle Biosciences, Inc. (CSTL) carries a lower debt/equity ratio of 8% versus 31% for Exagen Inc. — giving it more financial flexibility in a downturn.

By revenue growth (latest reported year), Exagen Inc.

(XGN) is pulling ahead at 19. 7% versus 3. 7% for Castle Biosciences, Inc. (CSTL). On earnings-per-share growth, the picture is similar: Exagen Inc. grew EPS -12. 0% year-over-year, compared to -233. 9% for Castle Biosciences, Inc.. Over a 3-year CAGR, CSTL leads at 35. 9% 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.

Castle Biosciences, Inc.

(CSTL) is the more profitable company, earning -7. 0% net margin versus -30. 0% for Exagen Inc. — meaning it keeps -7. 0% of every revenue dollar as bottom-line profit. Operating margin tells a similar story: CSTL leads at -12. 4% versus -21. 1% for XGN. At the gross margin level — before operating expenses — CSTL leads at 68. 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.

None of the stocks in this comparison currently pay a material dividend.

All are effectively zero-yield and should be held for capital appreciation rather than income.

For long-horizon retirement investors, Castle Biosciences, Inc.

(CSTL) is the stronger choice — it scores higher on the combination of lower volatility, dividend reliability, and long-term compounding (low volatility (β 0. 88)). Both have compounded well over 10 years (CSTL: -10. 1%, XGN: -84. 2%), 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: XGN is a small-cap high-growth stock; CSTL is a small-cap quality compounder 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.