Come on, Chuck, being a technology type, I reckon you can do better than that. You are right but for the wrong reason.
The answer is that the halogen also produces some visible light as well as heat, so it is not 100% efficient at converting all the input power into output heat.
Purely electrical heating devices are unique in that all the input power gets turns into heat and they are 100% efficient at doing that. (That situation is different from oil-fired or gas-fired appliances, where some of heat is lost up the flue). Therefore any heating elements - irons, toasters, electric bar fires, oil-filled rads are identically efficient - they are all 100%. That doesn't make them cheaper to run than a gas fire (not the situation, I know) because electricity is so much more darn expensive than gas or ful-oil in the first place.