It's hard to pick but I think Gambhir's innings was better. When India was 31/2 the pressure was massive and he was the one who had to absorb it. There was still some pressure when Dhoni came in but not nearly as much.
And yeah Gambhir has been fantastic over the last few years in pressure situations. I have always been skeptical about his technique against fast bowlers in test matches and still am to some extent but there is no denying his ability to handle pressure.