The one on the right hand side is a Sanke X Showa F1
The one on the left hand side is a (Sanke X Showa F1) x (Sanke)
Although both are not high quality koi, but i hope you can see the different of the sumi.
"Sanke X Showa F1" has bigger sumi pattern, this koi is actually a by-product when a breeder trying to use showa's sumi to improve a sanke's sumi. I don't know why, i find this kind of koi's hi fade very easily.
"(Sanke X Showa F1) x (Sanke)" improved sumi, very black sumi and stable, also the hi is more stable than the "Sanke X Showa F1".
Please note that both koi never eat any colour enhance before.
The above is only my opinion, so if i am wrong please forgive me.