I prefer Ray's 1st method - Ferment to dry and then re-sweeten with
sugar and add sorbate (and sulphite). I've made a couple of real nice
Rieslings this way. With a little bench testing with small samples
before sweetening the whole batch, you can get the sweetness right
where you want it.

Haven't tried the cold method, but it seems to me it might be difficult
to hit your target sweetness -you'd have to keep testing all the time
to make sure you didn't go past the level you wanted - then you'd have
to chill very quickly to make sure you kept it where you wanted it.
Easier to ferment dry and resweeten imho.