Jbill311 I understand your statement and I see what you are saying. There is a point you are missing and I will try to give you an example to help you to see the point I am making.
There is not one powerful dark side user that I know that was not trained in the dark side. One uses dark side energies (these being emotions such as anger, fear, etc) to focus them into powerful and deadly attacks. This is more than just a boost to ones current state such as tapping into the dark side.
Exar Kun as a light user tapped into the dark side to escape being trapped under a large pile of rocks after a cave-in occurred. His pride and ambition overwhelming him, Kun refused to accept death, calling upon his rage and hatred to fuel the dark side within, temporarily escaping his fate. Please note Exar Kun had not fully changed at this time.
Once he embrace the dark side fully he became a totally different person. One thing of note, he received training in the dark side. His force abilities even style of fighting changed.
Let us look at Anakin. Anakin used the dark side against Dooku and won.
Did he change as a person? No.
Was he focused when he fought Dooku? Yes, he had two lives to save.
Anakin vs Obi Wan:
At this time Anakin had already embrace in full the dark side. He had changed as a person. Please note that Anakin had not yet been trained by Sidious in the dark side. Nothing changed about his style of fighting or his force abilities. What did change was the type of person he was which would affect him as a duelist.
As was stated in previous post of ours Anakin reasons for fighting Obi Wan were different from his reasons for fighting Dooku.
Here is the point, Anakin as a light user whether he tapped in the dark side or did not was a more focused and controlled duelist who used his training and power to his advantage with engaging in a duel or battle. As a dark user of the force Anakin was not a controlled or a focus duelist because he was no longer the same person and rely purely on his emotions to over power an opponent.
Even the movies depict this well in the way Anakin fights Dooku in comparison to the way he engages Obi Wan.
If Anakin had received any type of training from Sidious for any length of time he mostly likely would have destroyed Obi Wan.