Hi Gilbert, I have always pruned
trees late in the winter dormancy. Just when the sap begins flowing upwards, before buds.
There may be advantages to both methods. It seems if the trees are budding, then it may shock a tree to prune just when it wants to bloom.
That's our method. If light trimming is the goal, then perhaps while in bud is ok. A hard prune would seem to be better before buds.
Hope this helps and hope others chime in too.