Neither really gives off much heat at all. I can practically grab the bulbs for like 5 seconds before it becomes uncomfortable. But in terms of your question I'd say the 2 - 23 watts as although the watts are only a bit more, its really the fact that you have 2 which is creating that much more wasted heat energy. But when you look at the larger picture, CFLs barely put off any heat at all. At least compared to other bulbs.