SELX vs ACLS vs ONTO vs MKSI

For growth investors, MKS Inc.

(MKSI) is the stronger pick with 9. 6% revenue growth year-over-year, versus -67. 9% for Semilux International Ltd. Ordinary Shares (SELX). Axcelis Technologies, Inc. (ACLS) offers the better valuation at 41. 8x trailing P/E (43. 5x forward), making it the more compelling value choice. Analysts rate Axcelis Technologies, Inc. (ACLS) a "Buy" — based on 12 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, Axcelis Technologies, Inc.

(ACLS) is the cheapest at 41. 8x versus Onto Innovation Inc. at 98. 6x. On forward P/E, MKS Inc. is actually cheaper at 30. 4x — 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: Onto Innovation Inc. wins at 1. 12x versus Axcelis Technologies, Inc. 's 2. 06x — a reasonable growth-adjusted valuation.

Over the past 5 years, Onto Innovation Inc.

(ONTO) delivered a total return of +312. 6%, compared to -94. 4% for Semilux International Ltd. Ordinary Shares (SELX). Over 10 years, the gap is even starker: ACLS returned +1506% versus SELX's -94. 4%. 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), Semilux International Ltd.

Ordinary Shares (SELX) is the lower-risk stock at 0. 30β versus Onto Innovation Inc. 's 2. 66β — meaning ONTO is approximately 798% more volatile than SELX relative to the S&P 500. On balance sheet safety, Onto Innovation Inc. (ONTO) carries a lower debt/equity ratio of 1% versus 173% for MKS Inc. — giving it more financial flexibility in a downturn.

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

(MKSI) is pulling ahead at 9. 6% versus -67. 9% for Semilux International Ltd. Ordinary Shares (SELX). On earnings-per-share growth, the picture is similar: MKS Inc. grew EPS 55. 5% year-over-year, compared to -436. 9% for Semilux International Ltd. Ordinary Shares. Over a 3-year CAGR, MKSI leads at 3. 5% 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.

Axcelis Technologies, Inc.

(ACLS) is the more profitable company, earning 14. 3% net margin versus -152. 3% for Semilux International Ltd. Ordinary Shares — meaning it keeps 14. 3% of every revenue dollar as bottom-line profit. Operating margin tells a similar story: MKSI leads at 14. 4% versus -228. 8% for SELX. At the gross margin level — before operating expenses — ONTO leads at 49. 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, Onto Innovation Inc. (ONTO) is the more undervalued stock at a PEG of 1. 12x versus Axcelis Technologies, Inc. 's 2. 06x. A PEG below 1. 5 suggests fair-to-attractive pricing relative to expected growth. On forward earnings alone, MKS Inc. (MKSI) trades at 30. 4x forward P/E versus 43. 5x for Axcelis Technologies, Inc. — 13. 1x cheaper on a one-year earnings basis. Analyst consensus price targets imply the most upside for ONTO: 12. 5% to $308. 33.

In this comparison, MKSI (0.

3% yield) pays a dividend. SELX, ACLS, ONTO do not pay a meaningful dividend and should not be held primarily for income.

For long-horizon retirement investors, Semilux International Ltd.

Ordinary Shares (SELX) is the stronger choice — it scores higher on the combination of lower volatility, dividend reliability, and long-term compounding (low volatility (β 0. 30)). MKS Inc. (MKSI) carries a higher beta of 2. 64 — meaning larger drawdowns in market downturns, which matters significantly when you cannot wait years for a recovery. Both have compounded well over 10 years (SELX: -94. 4%, MKSI: +750. 6%), 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 Technology 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.