No one in their right mine runs billet for one simple reason. Weight. They aren't more durable. They bend and stay bent instead of bouncing back, they don't provide any benefit what so ever.

As for shock towers, it depends on the track conditions. For low bite and bumpy you will see some switch to carbon/graphite for more flex and give to help keep/increase traction. High grip and smooth, run aluminum to keep the suspension tighter and more planted. They are tuning options not for looks

Only thing billet bling is for is the Bashers who like shiny. Even in the bashing world serious people run rpm not billet.