Granted’s line is “The easiest way to access your cloud” and “Seamlessly swap between AWS accounts.” It is free and open source. It helps once identities and profiles already exist.
Quiverstone is for a portfolio of unrelated client AWS Organizations. The client often hands you a cross-account role, not an Identity Center or a profile file.
Profile managers and Granted help once identities exist; they don’t help when the client only gives you a cross-account role. Quiverstone enrolls that Org, lists its accounts, and assumes the role with External ID. The session uses your browser and shows up in their CloudTrail.
No. If you already have profiles or SSO for one fleet, keep using them. Quiverstone is the inventory and assume-role path for client Orgs that are not in that identity store.