I greatly prefer being able to suspend/resume - you have all the state of your applications, down to cursor position in documents, history and scrollback in shells, etc. While Linux's session management is very nice it can't replicate all this, so faster boot doesn't help as much as getting suspend working - I usually don't bother trying to make it work as it's quite a hassle compared to hibernate.
I don't find memory leaks an issue these days - Firefox still crashes enough (due to plugins mostly) that it clears out any leaks in any case.