"Repairable" vs. "reparable" vs. "irreparable" vs. "unrepairable"

Solution 1:

Pretty much. Repairable seems to be becoming more popular than reparable, having once been less popular, presumably because one can "piece it together" rather than having to learn the word.

More interestingly, Irreparable is much more popular than the rest put together, seemingly largely because it has a legal meaning and is often used in hyperbole and analogies.

Solution 2:

The one difference I would suggest is that repairable and unrepairable generally refer to things which are broken; reparable and irreparable (as commonly seen in the phrase "irreparable harm") generally refer to the damage that has been done to those things.

Examples:
- My client's reputation has suffered irreparable harm.
- I dropped my phone in the toilet; it's basically unrepairable.