Ogive shape, materials & method of construction and impact speed will be more of a restricter to penetration than SD when they are so close, I would guess.

Due to the more pointy shape of the .577's, I would suspect similar constructed and velocity .577's would penetrate more deeply.

How much penetration is needed? The more blunt, rounded & larger diameter bullet will impact with more effect. This is why round balls are so effective on game than mor epointy elongated bullets.

As long as penetration is sufficient for the use, the larger diameter blunt bullet will hit 'harder' & have more 'effect' on the animal.

Either will probably detach your retinas with enough shooting.

Of course, I course I have neither and therefore, agree whole heartedly with Allen.