In my opinion, being good and just on time is extremely important and is far better than being perfect but late. This is because time is an extremely important factor that which many people tend to ignore. Submitting your due assignments or tasks on time represents both loyalty, reliability, and is always considered as a sign of good performance.
On the other hand, even if you are perfect but late, chances are that your perfection will usually get overshadowed by the fact that you were late and hence, your overall performance will not be rated high enough. This is a fact!