Answer:
In most cases, neither. A disciplinarian parent is probably an ineffective parent, because their child is more likely resist either voluntarily or subconsciously to authority that is deemed excessive. A "best friend" parent is likely ineffective because they will altogether lack the authority necessary to properly raise and educate a child. A child needs reasonably strict guidance and restrictions in addition to freedoms and privileges. This will lead to a more balanced upbringing and a more balanced product (child). In short, the best is something between the two.
I tend to lean more towards the former, simply because a parent and a best friend are usually two altogether distinct positions in a child's life. Not always, of course, and it largely depends on the individual relationship. Additionally, that is not to say that parents should not be close to their children (perhaps closer than a best friend, since a parents presumably lives with their child). But their purpose, their role, and their "hierarchical status"/authority is unique to each position.
Step-by-step explanation:
Just my opinion, but I hope it helps :)