I'm a novice looking at the same thing for my first shot at a novel.
Journal / Diary style seems very good for my personal voice and particularly for a story I wish to tell about scientific exploration and adventure. It also allows you to highlight emotions, feelings, reflections, etc. at different points of the story (assuming you have the in-story author writing an entry at a time instead of a lump-sum document at the end of the story).
The disadvantages can be tricky, I feel: yes, the blow-by-blow can be hard to convey, but perhaps more than that, the dramatic tension of interpersonal conflict is much harder to achieve without live dialog between two characters in conflict.
Imagine trying to tell the finale of Star Wars Episode III: Revenge of the Sith where Anakin and Obi Wan are locked in conflict as an after-the-fact diary. Maybe you can do it, but you're going to suck the emotion and tension out of the scene, not just because it's not live, but because we know that the writer is writing it after the fact and therefore must have survived.
Of course, I think diary style approaches can be very useful for twists by relying on either an unreliable narrator (omitting things - particularly about the narrator's own actions, exaggerating, lying, etc) or deceiving the audience about the nature or purpose of the diary / story, only for it to have a new meaning at the end of the story when accompanied by an appropriate twist ending.
I'm going to give it a shot, but I'm worried about two scenes of intense ideological opposition, and think I ought to research how other writers have solved this problem in their own works. I recall reading a few books where authors changed modes a bit and had the narrator say something like "What happened next happened very quickly, but I will do my best to describe it to you as it happened".