SMG will be faster as it can change gear fast than the human hand. Maybe the SMG car had a fault somewhere, theres a lot of difference depending on how a car has been run in or used generally.

It's worth pointing out though that SMG is still fundamentally the same box just with actuators on the selector and clutch.

As for which is best, your drivng style will depend that. And it's established that SMg can be "fun" when trying to park.