I've decided that instead of saying "sure as hell", which is a common expression that flows out my mouth quite easily, I'd like to start saying "sure as shit".
The alliterative factor is a big part of the reason. Furthermore, "sure as hell" doesn't necessarily make a whole lot of sense if you take it literally. Many halfway religious people who have not-super-well-defined spiritual leanings might believe in some kind of afterlife, but a lot of them wouldn't think of hell as any kind of certainty. I think people nowadays are probably a lot more skeptical about the existence of hell than they are about some vague kind of afterlife or some kind of sentient superhuman force that can guide our lives.
Obviously, though, an expression like "sure as hell" shouldn't be taken so literally. When people say it, they aren't actually saying that the existence of hell is something they're more sure of than anything. It's a bit like when people say "What the fuck?" They don't actually mean "What in the name of sexual intercourse?" It's more like saying, "What in the name of [strong word for emphasis]?"
Language in general is fascinating, and so is swearing in particular. I could talk about it all day (for instance, it's interesting that "shit" is a stronger word than "hell", even though the former is merely a perhaps unpleasant daily reality, whereas the latter is punishment until the end of time). But at any rate, yeah, "sure as shit" rules.