I say "inedible" myself. I've never used either of other two.
And I use it to mean that it's too bad to merit being eaten, not that your body simply cannot process it. For that, I'd say "it can't be eaten" not "uneatable."
A rock is something that can't be eaten. (Swallowed, yes, but eaten, no.)
A soup that soup that someone put a cup of salt in instead of a teaspoonful would be inedible.
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