Ovens - fan on or off?

I have a new cooker (a Smeg), a huge improvement on my increasingly erratic former model. The electric oven is much more efficient and reliable.

The fan made cooking our Christmas dinner, with its various components, a great deal easier. But I haven't worked out yet whether the fan is worthwhile for cooking individual dishes, and various online forums do not give a clear answer: while everyone knows that you should use a lower heat when cooking with the fan than you would otherwise, no one seems clear on whether the fan improves the baking process or whether it tends to dry out the food. And if I put a dish under the grill, will it brown more efficiently with the fan on or off?

Yesterday, I used the fan when cooking a toad in the hole. It worked brilliantly: the batter rose, and was light; and the sausages were as juicy as we could have wished. But would the conventional, non-fan setting have produced just as good a result?