I think it's all about sincerity. Uke as the initiator of attack should have full commitment and intention to prevent nage doing technique, but uke should bear in mind that uke's action is to help nage executing the correct technique, not to resist or beat nage in pride.
Same thing goes for nage. Nage as the reactor of uke's attack should move efficiently to change disadvantages situation into an advantageous one. But nage also has to bear in mind that his/her objective is just to 'turn the table', not to injure, maim, or kill the uke.
So I said here that there's nothing as uke or nage is always right, as in aikido the relationship between uke and nage is mutual.
anyway, those pros and cons is right, wynand. But I don't suggest to go full force when your partner is still a newbie, go slow and soft first then after they have some experience we can increase the speed and power, the higher the experience the higher level of speed and power you can apply.