Honey vs sugar
Swapping one for the other changes four things at once — sweetness, moisture, colour and pH — which is why it is not arithmetic.
The short answer
Sugar is a dry crystalline solid that provides structure, aerates when creamed and browns predictably. Honey is a hygroscopic acidic syrup that browns early and holds water. Replacing one with the other by weight therefore changes sweetness, moisture retention, colour and acidity simultaneously, and the changes do not cancel. In practice a honey-sweetened bake browns sooner — often before the centre is set — keeps soft considerably longer, and reacts differently with a bicarbonate-based leavener because honey supplies acid the formula was not expecting. Honey’s water content is real and does NOT make the formula wetter: the sugars hold that water and compete for whatever else is present, so the dough usually behaves stiffer than its liquid suggests.
Where they differ
| Dimension | First | Second |
|---|---|---|
| Physical form | Syrup — cannot cream, cannot provide crystalline structure. | Crystalline solid — creams, and provides structure. |
| Browning | Fructose browns at a lower temperature; colours early. | Predictable, later browning. |
| Moisture behaviour | Strongly hygroscopic; keeps bakes soft for longer. | Hygroscopic, considerably less so. |
| pH | Acidic; interacts with bicarbonate of soda. | Near neutral. |