Each concept needs to convey different things or solve specific problems but there is always a narrative being them. An environment tends to require more thinking. There is the composition, the mood, lighting, and the design. Sometimes there are multiple narratives in one single shot which make it more challenging. A ship is more direct but still need to have all the proper elements to feel right and fit the story.
For this project I use 3D much more than usual. I like doing that when certain designs are complex or need to be very precise like ship design and weapons or the palace interior. There is also a different creating process I like when using 3D. It allows me to come up with intricate shapes that would be very difficult to conceive in 2D. The lighting is also important and using 3D makes it a lot easier. I usually built 60 to 80% in 3D and finish the concepts in Photoshop.