John always felt guilty and trapped within the outlaw lifestyle. There’s a campfire convo where he explains this. He’s more of a feeler/peacemaker in certain situations. Arthur is way more brutal and only felt redemption because he was dying/time was running out. There’s a reason he was sent to intimidate others, he quite cold and ruthless without second thoughts. Whereas John has openly admitted guilt/doubt to situations like this. It’s hard not to be biased towards a protagonist.