My issue with Firefox is essentially one bug where they refuse to fix. In private mode, previously closed tabs are, for some reasons, restorable. This doesn't happen for Safari or Chrome.
It tricks you into thinking that session state is kept only per-tab by disabling a useful feature (history), however the incognito session's state is actually scoped per-window and not properly cleared/forgotten until you close the window.
Firefox knows how to have temporary window-local cookies/site data _and_ history. Chrome doesn't know how to keep the history. It's a missing feature IMHO.
I prefer this behaviour of limiting the browsing history per tab per session instead of the way Chrome implements it