I think its a question of what your actually watering ? I agree with Sacha in that, I never water in the winter in the evening, always in the morning, so that as Sacha says, the foliage can dry out before dark but of course as nuserymen, we are watering plants in pots ! In open ground, you probably wont be watering in winter anyway ? so, in summer, I agree, evening seems to do a better job !
If using a liquid feed, it goes without saying that you never feed with the sun on the leaves, so again evening gives much safer and better results, especially if like me you use 'miracle grow' which will folia feed as well !
Then theres the question of how often, someplants like Aeonium, Agaves, Sempervium and like minded succulents like to really dry out before being watered, especially in pots ! If you keep this type of plant continuosly damp, they wont root or grow very well. Given our experiences of the recent winters, its my opinion that with alot of 'exotics', the drier they are in winter, the more cold they seem able to withstand.
Lannerman