I haven't looked at Gargantia myself, with the exception of Knights of Sidonia and Gundam 00, I don't generally like giant mecha anime. I've watched the first two episodes of Psycho Pass and while the story is pretty good and the animation is good, I just absolutely hate the premise of the show. "Oh, you have criminal thoughts? Deadified! Associated with a criminal? K-worded!" Not my cup of tea. I really enjoy Studio Ghibli movies, but haven't seen Arietty yet, despite having a boxed set of all/most of the Studio Ghibli movies. I totes forgot that Nausicaa was a manga. I've never read any of Irving's novels/works, would you recommend them? Aside from the various manga I'm reading, I currently reading notes from a small island by Bill Bryson.
I think Psycho Pass' premise presents a really interesting moral scenario. If you had a system that could always detect violent criminals (non-violent criminals are simply locked up), is it a reasonable thing to use deadly force against them? What does that do to society? It's very death note-esque. If you like sci-fi anime then I would recommend giving it another look and try focusing on the potential utilitarian morality of the premise rather than its immediate distaste.