I too do believe that both played an important interior motive in the games. I believe that the truth is more important than the ideals. Team Plasma had many ideals and beliefs on Pokemon and they thought that they were doing the right thing, but the truth is that the were evil and were harming the Pokemon world. I think the truth is more important because characters can get blinded by their ideas and beliefs, and do what they feel is right. Their ulterior motives could be wrong. A good example is N; he believed that his actions were righ and justified. He loved Pokemon so much that he could talk to them and feel for them. He believed that all Pokemon should be free, but he didn't realize what he was doing was wrong until you had freed him from his evil thinking, and made him see the light. He learned the truth and that changed him .The truth was a lot more important than his motives. His motives drove him to do wrong; realizing the truth, he did right.
I think that motives were more central to the game's core. I believe that the Pokemon franchise is based off of motives. You, the trainer has the motive to do good and bring tranquility to the Pokemon world. Your dream is to become and Pokemon master and to defeat your rival. Your motives is that you have to prove something, and you travel all throughout your region to catch Pokemon, win badges, and prove that you're a superb trainer.
The last question, I have no idea for Black/White. I think Mewtwo is a good example on how motives can lead to wrong doings. Mewtwo had believed that all humans were evil, and his motive was to destroy the human race and to rise Pokemon to superiority over humans. Mew helped mewtwo to realize the truth, allowing him to change his ways.
Deep questions, sorry if I didn't answer them correctly.