An insert goes into an existing masonry fireplace opening. A stove stands free in the room on its own hearth. That is the actual difference, and it means the question usually answers itself based on what your house already has.
Both are efficient wood-burning appliances. Both need a correctly sized liner. Both are governed by air district rules on what may be installed. The comparison is less about performance than about fit.
The Case for an Insert
If you already have a masonry fireplace that you rarely use because it loses more heat than it gives, an insert is usually the more sensible route.
An open masonry fireplace is a poor heater. It draws a large volume of warmed room air up the flue, and on a cold night the net effect can be to cool the house. An insert closes the opening, contains the fire, and turns a decorative feature into something that actually heats.
It also uses a structure you already have. The masonry opening houses the unit and the existing chimney carries the liner, which means no new penetration through the building.
The Case for a Stove
A stove radiates from all sides. Standing in the room rather than recessed into a wall, it puts heat out in every direction, and for heating a space properly that is a genuine advantage.
It also does not require an existing fireplace. If the room where you need heat has no masonry opening, a stove with a properly installed flue is the option that does not involve building a fireplace first.
The cost is floor space and clearances. A stove needs specified distances from combustible materials and a hearth pad beneath it, and in a small room those requirements can be the deciding constraint.
The clearance and hearth requirements are covered on the wood stove services page.
Both Need a Liner
This is the part that gets left out of the comparison and it matters to the budget.
An efficient appliance vents at a lower temperature and a lower volume than an open fire. A masonry flue sized for an open fireplace is generally far too large for it, and an oversized flue makes gases slow down and cool, which is precisely the condition creosote forms in.
So both an insert and a stove connected to an existing masonry chimney normally require a correctly sized liner running the full height. It is not an upsell; it is what makes the appliance work as intended.
If a quote for an insert or stove installation does not mention the liner, that is worth asking about directly. It is the single item most likely to be missing from an optimistic estimate.
What the Air District Allows
California air districts restrict what wood-burning devices may be installed, generally requiring certified clean-burning appliances for new installations and replacements. The specifics differ by district.
This constrains the shortlist before preference gets involved, and it is worth establishing at the start rather than after choosing an appliance.
Fuel Matters More Than the Choice
Whichever you install, the thing that will most affect how well it works is the wood you put in it.
Unseasoned fuel spends the fire's energy boiling off water rather than heating the room. The result is poor output, glass that blackens within the hour, and heavy creosote in the flue. No appliance and no installation overcomes it. Properly seasoned wood is the cheapest improvement available and it is worth sorting out before spending anything on hardware.