CSGP vs Z: Which Is the Better Buy in 2026?

Same yardstick, side by side (as of August 2026). Valuation lined up like this is most meaningful for two names in the same corner of the market, which these are. Figures are approximate; verify before investing.

Reading it: Z is the cheaper of the two on forward earnings, but cheaper is not the same as better. Pair the valuation with growth (how far the forward P/E sits below the trailing P/E) and risk (beta) before you decide.

The metrics above tell you which is the marginally better business. The bigger risk for most people is not picking the slightly worse stock, it is over-concentrating. CSGP and Z share themes, so owning both, or adding either to what you already hold, can quietly push a large share of your portfolio into one bet.

This is the part a generic comparison page cannot answer, because it depends on what you own. Connect your brokerage and Walnut shows your real, combined CSGP and Z exposure, flags overlap with your existing positions, and tells you if adding one would tip you past a concentration you are comfortable with, read-only by default, with your login staying at your broker. Walnut is not an investment adviser.

CoStar Group is a real-estate information, analytics, and online-marketplace company. Its core commercial franchise sells subscriptions to the CoStar database (property records, leasing, sales comparables, and analytics compiled by hundreds of researchers), LoopNet (the most-visited commercial listing marketplace), and Apartments.com (the leading multifamily rental marketplace). More recently the company has pushed into residential real estate with Homes.com, spending aggressively on marketing to challenge Zillow and Realtor.com. Revenue is largely recurring and subscription-based, which historically produced high margins and consistent growth across dozens of quarters.

Full CSGP guide

Zillow Group, Inc. operates the largest online real estate marketplace in the United States, drawing hundreds of millions of monthly visits across the Zillow, Trulia, and StreetEasy brands. Its business has three pillars. Residential (its For Sale core) connects home shoppers with agents, earning mostly through Premier Agent and Showcase. Rentals monetizes multifamily and single-family listings through advertising and lead generation. Mortgages, run through Zillow Home Loans, originates purchase loans and ties financing into search. Zillow is a marketplace and software company, not a homebuilder or iBuyer, so its revenue tracks how actively people transact rather than the value of homes it owns.

Full Z guide

Both fit overlapping themes, but they are not interchangeable. The useful comparison is which set of drivers and risks you want exposure to.

• CSGP drivers: Commercial data moat and pricing power; Residential expansion with Homes.com.
• Z drivers: Housing super app and enhanced markets; Rentals as a growth engine.

A faster-growing, richer-valued name usually swings harder, so it suits a longer horizon and a higher tolerance for volatility; a steadier, more cash-generative business suits a more conservative or income-minded investor. The honest test is which set of risks you could hold through a drawdown: Reported profitability has been thin because of heavy Homes.com marketing, so the residential bet remains unproven and could keep depressing margins if audience and agent revenue disappoint. For Z, the dominant risk is housing cyclicality: with existing-home sales near multi-decade lows on elevated mortgage rates, Zillow's Residential and Mortgages revenue depend on a depressed transaction market, and a further slowdown or rate shock could stall growth.

Pick CSGP if you believe its drivers more; Z if you believe its. Many investors hold both, but since they share themes, that is a concentrated bet, not diversification. Decide deliberately and check overlap. For the full detail, see the CSGP and Z guides.

CSGP. CoStar carries a very high trailing P/E because heavy residential spending has kept net income small relative to its size, so the forward multiple is a more useful gauge. Revenue keeps compounding at double digits and 2026 profit guidance was raised, pointing to a possible margin inflection. The valuation reflects the market pricing in a successful Homes.com build-out rather than current earnings.

Z. These characterizations are qualitative and tied to the asOf date; verify live figures before acting. Zillow is best understood as a growth marketplace stock, so investors tend to weigh revenue growth, segment mix (Rentals and Mortgages versus Residential), and EBITDA margins more than a headline P/E, which can be distorted while the company transitions from GAAP losses to profits. Because there is no dividend, the entire return case rests on growth and eventual free cash flow rather than income.

Headline figures (approximate, July 2026): CSGP shows revenue (ttm) ~$3.5 billion, 2026 revenue guidance ~$3.78-3.82 billion (16-18% growth), q1 2026 revenue ~$897 million, up ~23% year over year, adjusted eps guidance (2026) ~$1.32-1.39; Z shows revenue trend Growing at a strong double-digit pace year over year in early 2026, led by Rentals and Mortgages with a steady Residential base, profitability Reached full-year GAAP profitability, a milestone after years of accounting losses; still reinvesting heavily in Rentals and Mortgages, margins Adjusted EBITDA margin has been expanding into the mid-20s percent range as the model scales; watch the trajectory, not a single quarter, dividend None; Zillow pays no dividend and returns capital mainly through share repurchases, so total return depends on price appreciation.

CSGP and Z are related but distinct: same themes, different businesses and risks. Neither wins in the abstract; the right pick is whichever thesis you actually believe, sized so you are not over-concentrated in one theme. Walnut can show your combined CSGP and Z exposure against your real portfolio. It is not an investment adviser.