If budget is not an issue, then it is always better to purchase a new car.
The reasons are:
1) You get it all brand new, and you get all the procedures done in a proper way.
2) You get the customer support and maintenance
3) Your insurance also runs in a proper way
4) You have lesser chance of being fooled and cheated.
But starting with an old car isn't a bad option either because
1) You are not burdened with a huge amount of money
2) To experiment on novices, it will bring down the amount of loss.
3) You save money while you get the desired model.
But before making a choice, you should make the security as the first criterion.