english is not my main language so I may incorrectly interprete this "lowlife" thing you are talking about. pardon me in advance.
I understand the two fish came from the same batch so I will assume they both got equal care. From the pic, Ray's showa is definitely bulkier than yours which should indicate that it is a better eater. At least from the pic, the overall head size and shape, eye distance, width of the mouth, shoulder width and curve, the angle from gill plate to tail stop all looks good on Ray's showa. The other showa, the mouth look somewhat pointy (could be pic angle), shoulder width and curve not wide enough (again could be pic angle), angle from gill plate to tail stop looks too step (and again could be pic angle). So, to answer your question, it's not only abut the size of the head.
But hey, they're both still small fishes and nothing is certain in small kois. What I can tell is that both fishes are so much better than my Dainichi showa attached. It's only 18cm.