Legalidad en California
Both are CFTC-regulated and legal in all 50 US states including California. Polymarket offers US event contracts through its acquired CFTC-licensed exchange. Sleeper operates event contracts under CFTC oversight. No state-level differentiation for California residents.
Mercados y cobertura
Sleeper covers NFL, NBA, MLB, NHL, soccer (including World Cup 2026), and select cultural markets — sports-anchored throughout. Polymarket's global product is famous for political, cultural, and macro depth, but its US product currently leans toward sports while broader verticals roll out. Sleeper is the deeper sports book today; Polymarket is the deeper everything-else book once its US expansion completes.
Precios y comisiones
Both charge modest per-contract fees disclosed at order entry, with no built-in house margin like a sportsbook. Polymarket's US fee structure is still being finalized publicly but has historically been low offshore. Sleeper's fees are in a comparable range. On liquid sports markets, effective cost is similar.
Experiencia de usuario
Sleeper's interface is social and fantasy-anchored — your league, draft, group chat, and event contracts all sit in one app. Polymarket's interface is chart-forward and news-rich — visual probability curves, context, and community commentary. Two very different reasons to open the app.
Quién debería usar cuál
Use Sleeper if: you already use it for fantasy, you primarily trade NFL or NBA game-by-game, you want trading and group chat in one place. Use Polymarket if: you want exposure to its global cultural and political markets as US coverage expands, you value chart-rich context over social features, or you eventually want a non-sports prediction market home base.