It took me a few moments to figure out that these were two photos, so the first thing I would do is maybe rotate them so they are horizontal and then put a bold line to make the two different photos obvious.
You are right though, these pictures are almost identical but with many distinct differences. These are gorgeous shots and you are very talented and very lucky to be able to capture these when you did. On the photo on the right I love how you can see purple on the clouds! These pictures are really breath taking thank you for posting these
Originality - nailed it. I've yet to see this done. While I think this is an utmost silly concept, its executed flawlessly, and the end result is stunning. Mabey to the point we should be re-writing the book on silly.
Technique - if it didn't come out so awesome I'd probably be scolding you for the horrible idea of combining two horizons. Combine with defining center black line splitting two uneven halves of the photo, should be a technical foul. Its pulled off stunningly, and the two sides seem to merge as a continuation of eachother rather than two separate entities
Lighting - big one for me personally, lighting can really make or break a picture. Lighting is excellent. Colors are vivid and strong. The cool but intense purple tones contrast and nicely compliment the warm yellows and oranges.
subject matter - taking an already intense sunrise/set and making it look truely unworldly as some sort of nebulae or intergalactic phenomena