Compare reverse osmosis water vs distilled water at the level of what actually happens to the molecules and the differences stop being marketing. A membrane separates by size and charge under pressure. Distillation separates by boiling point. Both leave you with water that is very low in dissolved solids, and each has a category of contaminant it handles poorly for reasons built into the method.
Two different physical separations
In reverse osmosis, household pressure pushes water through a semipermeable membrane while dissolved salts and larger dissolved species are held back and flushed to drain. In distillation, water is boiled and the vapor is condensed elsewhere, leaving anything non-volatile in the boiling chamber. The first is a continuous filtration process at room temperature; the second is a batch phase change that consumes heat.
What each one struggles with
Distillation is weakest on volatile compounds, which boil at or below the temperature of water and can travel with the steam, which is why serious distillers add a carbon post-filter. Reverse osmosis is weakest at the front end: it needs sediment and carbon prefilters to protect the membrane, chlorine damages certain membrane materials, and a fouled prefilter degrades performance long before anyone notices at the faucet.
Purity is not one number
People compare these two using a handheld meter that reads dissolved solids, and both will read very low. That reading says nothing about a volatile organic compound, nothing about bacteria, and nothing about whether the sample came from a properly maintained system. Treat a low meter reading as evidence that dissolved salts are gone, and use a laboratory test when you need to know about anything else.
Reading a claim on a box
Both technologies are sold with reduction claims, and the meaningful ones name a substance and a certified reduction against a recognized standard. A claim written as a general promise of purity is not testable. Look for the substances that appear on your own water report, and check whether the claim applies to the system as configured or only to a specific cartridge stack sold separately.
Questions people ask about reverse osmosis water vs distilled water
Is distilled water purer than reverse osmosis water?
On dissolved minerals they are close. Distillation can carry volatile compounds over with the steam unless the unit includes carbon after the condenser.
Does either process kill bacteria?
Boiling during distillation inactivates organisms, but recontamination in storage is possible. Reverse osmosis is a barrier, not a disinfection step.
Can I run a distiller on reverse osmosis water?
You can, but there is little point. The second process has almost nothing left to remove and simply adds electricity and maintenance.