Enamelled cast iron vs lined copper

Which one heats faster?

Lined copper, by a wide margin: the copper body of lined copper conducts at about 401 W/m-K against 52 for the iron body of enamelled cast iron. Conductivity is how quickly heat moves through the metal, so a high figure means the pan reaches an even temperature sooner and spreads the burner's heat across the base rather than concentrating it.

Conductivity is not the same as heat retention, and confusing the two is the most common misunderstanding about cookware. Cast iron conducts poorly at about 52 W/m-K and retains heat extremely well, because retention comes from mass and specific heat rather than from conductivity. That is precisely why iron sears well: the pan barely drops in temperature when cold food lands on it.

Which one suits which job?

Enamelled cast iron is best for braises, stews, beans, bread baking and anything acidic that needs hours of gentle heat. Enamel chips if the pot is knocked or dropped, and a chipped interior on the cooking surface means the pot should be retired from cooking. It also dislikes thermal shock, so no cold water into a hot pot.

Lined copper is best for sugar work, delicate sauces and anything where the pan must respond the instant the heat changes. Copper conducts about twenty five times better than stainless and roughly eight times better than cast iron. You are buying control, and paying for it in price, weight and upkeep.

Practical differences that decide it

Induction: Enamelled cast iron works on induction and lined copper does not work on induction. That alone settles the question for anyone with an induction hob.

Acid: Neither is reactive, so acidic cooking is fine in both. Oven ceiling: 500F against 450F, remembering that the handle usually decides the real limit rather than the material.

Weight and upkeep: enamelled cast iron is very heavy and lined copper is heavy. Neither requires seasoning.

The honest conclusion

Most kitchens should own both rather than choosing. They are good at different things, and neither is a substitute for the other. A mixed kitchen outperforms a matched one at every budget, which is the single most useful thing to understand about buying cookware.

If you genuinely have to pick one, pick on the job you do most often. For searing and browning, that is enamelled cast iron. For sauces and anything that needs quick control, lined copper spreads heat faster.