My 2 cents-
I use 0ne-step because it's all my LHB source has. It's worked okay, I've produced 1 decent batch of cider and one really tasty one, and 2 more healthily fizzing away. But I'd put some caveats on there:
One step is basically what they rinse dishes with at restaurants. It adds a bit of sanitizing and rinse power and isn't toxic. However as others have said, it chemically reacts as it breaks down, releasing oxygen. It also takes some stirring to dissolve the granules. This gives us two things to watch for: that you fully dissolve it so you don't have granules in your cider, and that you LET IT SIT. The jar does not list a safe lifetime before it stops releasing oxygen because that's not important for serving food, but probably an hour or more is safe. AND! Be sure you don't use too much, or it will leave residue. I usually err on the side of too little; if the water feels "Silky" that's enough.
Another caveat is that since one-step water breaks down to, well, just water, you CANNOT use it to fill your airlock like you can with some other cleaners. I just use vodka anyway.
So for me one step hasn't been a problem, but when I'm out i'll probably switch to a more foolproof agent. As it's been said above, they're all pretty cost-effective and one-step has too many buts. And I wouldn't use oxy clean since it's not for food or food surfaces.