Microsoft beats pricey Fortinet on AI growth and valuation

Both Fortinet and Microsoft have positioned themselves squarely in the path of artificial intelligence infrastructure spending, but their stock performance and valuations have created a puzzle for investors deciding which to own.

Fortinet's stock has been the clear outperformer, rocketing up 112% over the last three months. The company's management is explicit about the tailwind: "AI is a tailwind to drive the growth." They are seeing this directly in two ways—demand for securing new AI data centers and in protecting critical infrastructure. In operational technology (OT), a category focused on critical systems, billings grew over 70%. The company is winning large deals, with the number of contracts over $1 million（約1.6億円） increasing and total deal value growing over 60% in its last quarter. On the latest earnings report, Fortinet raised its full-year 2026 guidance for both revenue and service revenue, signaling management's confidence in its near-term order book.

Microsoft's exposure to the AI infrastructure boom is even more direct and extensive. The company both secures the infrastructure and builds its foundation. In its latest report, Microsoft disclosed that its "AI business surpassed $37 billion（約5.9兆円） ARR, up 123%." The Microsoft Cloud division, the engine of its growth, exceeded $54 billion（約8.6兆円） in quarterly revenue. Management projects "another year of double-digit revenue and operating income growth in FY '27," but underpinning that growth is a striking capital commitment: the company expects to invest roughly $190 billion（約30兆円） in capital expenditures in calendar year 2026. This commitment is the core risk an investor accepts when betting on Microsoft—the bet that this historic capital cycle will translate into the profitable growth the company projects.

The twist emerges in the trailing financial picture. Despite Fortinet's explosive stock performance, Microsoft is actually the faster grower, with 17.9% revenue growth over the last twelve months compared to Fortinet's 15.7%. Microsoft is also far more profitable, boasting a 47% operating margin versus Fortinet's 31%. Yet Fortinet trades at a price-to-operating-income multiple of 50.5, while Microsoft trades at a far more modest 18.2—meaning Fortinet is priced at more than 2.7 times Microsoft's multiple despite slower growth and lower profitability.

Fortinet's bull case rests on its focused execution, market share gains in cybersecurity, and that freshly raised guidance. The company's moat is built on its single, integrated operating system, FortiOS 8.0, and custom FortiASIC chips that the company argues provide a performance edge. The risk is that at 50.5 times operating income, the stock leaves no room for error. An analyst on the earnings call raised the specter of a post-COVID style "air pocket" if the current demand is a temporary pull-forward rather than a structural shift.

Microsoft's moat is built on the deep integration of its Azure cloud platform with enterprise workflows through Microsoft Copilot, creating immense switching costs. The central risk an investor must navigate is the disconnect noted by an analyst on the earnings call: there is "a bit of a disconnect that makes investors a bit nervous between how fast they're seeing CapEx growing and how fast they're seeing revenue growing." The bet is that $190 billion（約30兆円） in capital spending in 2026 will eventually translate into the projected returns.

Ultimately, the choice turns on what an investor is more comfortable underwriting: Microsoft's massive, but potentially high-return, capital spending cycle, or Fortinet's premium valuation in the hope its focused momentum can be sustained. The evidence currently favors Microsoft's combination of faster actual growth, superior margins, and a more reasonable price, though investors must believe the capital plan will pay off.

Both Fortinet and Microsoft are positioned to benefit from the historic build-out of AI infrastructure, but their paths and valuations have diverged significantly. Fortinet has seen its stock outperform dramatically—up 112% in three months—driven by strong execution in its focused cybersecurity niche. The company is winning large deals, with contracts over $1 million（約1.6億円） growing in number and total deal value up over 60% last quarter. Operational technology billings, a key category for securing critical infrastructure, grew over 70%. The company's recently raised full-year 2026 guidance signals management confidence in near-term order book strength.

Yet the financial fundamentals tell a subtly different story. Microsoft is the actual faster grower (17.9% revenue growth versus Fortinet's 15.7%) and far more profitable (47% operating margin versus 31%), yet trades at less than one-third the valuation multiple. Microsoft's AI business alone surpassed $37 billion（約5.9兆円） ARR with 123% growth, and its Microsoft Cloud division exceeded $54 billion（約8.6兆円） in quarterly revenue. The company is explicitly underwriting this growth with a colossal commitment: roughly $190 billion（約30兆円） in capital expenditures budgeted for calendar year 2026. This spending is the core strategic bet—management projects it will deliver double-digit revenue and operating income growth in fiscal 2027, but the path between massive capex and profitable revenue remains the central risk investors must accept.

For investors choosing between them, the decision hinges on confidence in forward execution. Fortinet's bull case rests on sustained market share gains, its integrated FortiOS 8.0 platform, and custom FortiASIC chips. Fortinet's risk is that its 50.5× operating income multiple leaves zero margin for error; any slowdown in AI-driven demand could be painful. Microsoft's advantage is scale, profitability, and the deep integration of Azure with enterprise workflows through Copilot—a moat that creates switching costs. But underwriting $190 billion（約30兆円） in capital spending requires faith that the return on that investment will materialize.