Doesn't really make much difference. The plant will branch anyway now that a flower spike has terminated the main trunk. You will get two maybe three new branches coming from just below where the flower stalk arises. If you want to remove the flower stalk, that would probably speed up the new growth.

A lot of cordylines are getting sick now due to hidden damage from the big frost last winter. I would remove the flower stalk, and feed it very lightly with a balanced food to encourage it to put on new growth. Either the top will start growing again, or it will put out new sprouts from the base, while the top dies.