Sam, I think the argument for using alternating half-hitches is that you don't expose the finished knot to a load in one direction. Supposedly, the alternating half-hitches lock it down more effectively. I think the best way I can describe this in terms of the lockdown and the burnt knob is that if it is tight, it holds together. If it has any wriggle room, then it will start to work itslelf loose under heavy loads. Once it has started to work itself loose, the continuing load will simply make it all fall apart.
It's like when you're pushing a car. How hard is it to get it moving but the moment it starts moving, it gets much easier to push. I can use the analogy of the half hitches to a hand brake and the knob to a brick in front of the front wheel of a car that is pointing down a hill. If you have a weak hand brake, it will provide resistance but it is not going to give you much confidence. Still, it it will hold unless you start rocking the car. On the other hand, that brick is is sitll there and you are going to have to really push it hard to try to get it over that brick. Even if the hand brake is weak, the brick may still prevent the car from moving. On the other hand, a really strong hand brake and brick as insurance will almost ensure the car does not move.
The simple reality is that I prefer twisted leaders. I have far more confidence in my ability to get a secure connection with this than I do with the single strand leader to braid. That said, I have to acknowledge that I have seen enough big fish caught on the single strand conenctions to know they work and they work well - provided you tie the knots properly. I have also seen enough failures with twisted leaders to know they are also prone to failure if you don't get the connection right.
I think at the end of the day, this comes back to a very simple principle and that is to ensure you become an expert at the knots you use.
