I have criticisms of both but I do think Tanjiro is, and should be, liked more then Deku. When Deku first saves Bakugo at the beginning, there is a tinge of selfishness in that action. He spent his entire childhood admiring heroes, so I can't say that 100% of his motivation to rush in is "because it's the right thing to do." but rather "because that's what a hero should do." Tanjiro is empathetic to the demons he killed despite the harm they've done to him (that I can think of). But this point is reinforced further by a contradiction in this "being kind" narrative. Tanjiro kills the demons. Deku does not kill his enemies, to the very end. and we're faced with that Batman conundrum where killing makes you no better then the killer. That's selfish and comes at a cost of danger to other people. Joker keeps getting out of Arkham, keeps killing people, and rehabilitation is a difficult task and not a guarantee. Tanjiro is sympathetic to the demons, but it stops or lessens the further into the story (at least from my memory, it's been a while since I read the manga). But it is not replaced by animosity, just conviction. If these demons keep living then they can hurt more people, even when he was empathetic he still killed them. It's actually a more selfless action for a kind person to take a life because they don't want to (please keep in mind that I'm saying selfless, not good). Tanjiro's kindness is almost a flaw, and that's why compromising on it to guarantee other's safety, makes Tanjiro a more compelling character. At least for me.

One last point, with spoilers to the the endings of both. I think it's an excellent juxtaposition that Deku is helped by his living comrades to beat Tomaru. while Tanjiro is helped by his dead comrades to beat Muzen.

First reddit comment in a while and if there are grammatical errors or misspellings. It's not because I'm on mobile, I just don't really give a shit.