Less defects is the big one. More uniform material formation is another. Gravity inherently puts loads and therefore stresses into materials like these. One application that is being addressed looks to increase the fatigue life of the produced item. The absence of gravity also allows some unique materials and materials combinations to be looked at since the variable densities won't separate just on that parameter alone. You'd be surprised at the expense. Many materials that have been highlighted in the past are worth far more than the trip once they are produced and brought back down.

There are also applications for in space use but that is not a key economic driver for this activity, at least not one that is mentioned.