Which are the leading browser-based single sign-on (SSO) portals available today, and how do they compare in terms of features such as authentication methods supported, integration with enterprise applications and identity providers, security and compliance capabilities, ease of setup and user experience, scalability for small to enterprise-level deployments, support for MFA and adaptive access, reporting and audit logging, customization options, performance and reliability, and overall effectiveness in simplifying secure access across digital environments?