The Sedna. As you saw, the color is rich, warm, recognizable as a precious metal and luxurious. With it's black dial, it is also the closest gold watch to a Speedmaster professional. The AML, stepped dial, dropped end chrono hand, long indexes, and even the aluminum bezel are all features of the early Speedys, not to mention the 105.012 style case. It is a Speedmaster that also happens to be in gold.
The Canopus is beautiful also. If I had to choose only one (which I did), the Sedna wins. Frankly, i don't understand the stealth wealth concept. If you want a gold watch, why try to hide it? It's one thing to say that you love the color of white gold, but why would a person buy a white gold watch because they were worried about what other people think?
Some people may not like gold watches. But for those who do, the Sedna is spectacular. IMHO, it is not only more attractive than the Canopus, but it is the most attractive gold Speedmaster to date, including the 50th Moonshine. It's main competitor is the new Moonshine Panda, which I haven't seen in the flesh, yet.
It is a difficult question when viewing pictures alone. But in the flesh, the Sedna truly stands out.