I can only give you my take (i.e. personal dogma that I'm not aware of any denomination affirming as official doctrine), but basically it comes down to the inherently negative effects of sin itself vs. the actual penalty contingent on knowingly indulging sin. My understanding of original sin is that Adam and Eves original sin introduced sin into a previously ideal world, not only earning them divine punishment for their acts, but inflicting sins inherently harmful effects, wholly apart from divine judgement, on the world (and, by extension, infected human flesh in particular with susceptibility to it). Original sin does NOT mean, as it's often understood to mean, that all of Adam and Eves descendants are guilty in Gods eyes of their initial sin. It DOES mean that their initial sin forever marred earths initial perfection and made it a place where truly awful things are now routine. The biggest, though not only, cause of that "banality of misery" is that because Adam and Eve infected their own bodies with sin, and because all their descendants are born into bodies directly produced from that flesh, every human being by definition inhabits a tainted vessel inevitably and continually separating man and God. That creates two phenomena:

1) Total depravity, of which you may have heard, and which makes isolation from God a certainty, along with eventual sin by anyone possessed of the awareness to be capable of it.

2) Suffering, decay and eventual death as a result of that isolation from the Creator and Sustainer of life.

Put more simply, I take original sin to mean sins presence in "carnal flesh" ensures isolation from God will bring everyone suffering and eventual PHYSICAL death, but SPIRITUAL deaths permanent total "separation from God" (the definition of Hell to which I subscribe) is due the fleshs susceptibility to temptation ensuring anyone capable of comitting their own sins ultimately will. Infants (among others) lack that capability and are thus not condemned by it (another function of Grace, I believe), but still inhabit the same corrupted flesh equally subject to physical suffering and death.

Hope that was reasonably coherent; again, just my take, I can't claim to represent anything more than my limited understanding of a matter on which there's little explicit doctrine and thus much debate. Interesting post to write while watching The Life of Brian, but since it's almost over and I've been up about 27 hours I think I should probably leave it there.