[PapaBear]

As mentioned before, I already posted this on he Malaysian forum, so here's what I said there.

You did well, as there ar no bad Koi in the group.
I would guess that #5 is quite likely male which will keep it a bit smaller, thinner in the future compared to the S3/S4. It will also finish sooner, which is probably part of the difference you are seeing in beni color as well as different bloodline.
My top 2 out of your original set are S4 and S3. I prefer S4 because of the body and pattern. S3 is very bulky now as a relatively young Koi, but the overly thick tailtube may indicate a problem in the future. Sometimes Showa develop a Kink in the tailtube as they grow old, and this one holds that possibility. S4 is not as thick today, but the body is very nicely conformed from nose to tail and as it matures it has much potential to grow large without deformity and become very thick as it goes above 65-70 cm.
Another thing to consider is pattern size and placement. As they grow the pattern will spread out and the color plates will move away from each other. S4 has a large enough pattern to mature into a nicely balanced adult. The others are all interesting in their own way, but above 70 cm I don't think the patterns will look well placed by comparison.
There's my 2 cents.