1. This question of Arjuna’s persists through chapters 3, 4 and now 5. He is not convinced that he should fight the battle and is trying his best to get Krsna to endorse his view that they should both retire to the Himalayas.
At a given level there appear to be contradictions. Rise to a higher level and they disappear. You gain clarity. When you understand a thing completely there are no doubts. When there is incomplete understanding confusion arises.
Krsna also has been advocating both action as well as renunciation. He concludes chapter 4 by powerfully telling Arjuna to be established in yoga. This adds to Arjuna’s dilemma. He does not understand that renunciation is the effect of right action. One cannot practice renunciation.
Arjuna is a rajasika person with many desires gurgling in his system. He has to follow the path of action. Only a person who has offloaded desires and is withdrawn from the world is fit for the path of knowledge.
2. Since Arjuna has not understood the line of reasoning so far he needs adesa instruction, not upadesa advice. So Krsna emphatically says the path of action is better than that of knowledge. However, this is meant only for Arjuna and is not a universal truth.
Most people are in spiritual infancy and are full of desires. In the modern world desires are encouraged, promoted and fuelled. In this scenario there are very few people who qualify for knowledge. The few, like Arjuna, who want to take knowledge as an escape route from unpleasant obligations are in a state of rajasika renunciation. They want to move away from action because of the pain associated with it, not for pursuit of the higher.