Final Form

An interesting new studying comparing a medium load (70% RM around 12 reps) and 1RM demonstrated as weight increased the allocation of muscle fibers changed. Meaning that during the 12 reps the pectorals (chest muscles) where stimulated more effectively and as the weight increased the anterior delts (front of the shoulders) started to take the load from the pectorals (% wise).

Therefore if you are training chest for symmetry or to directly isolate or grow the chest, then a 70% RM or 12 reps is recommended.

Reference

Król, H., & Golas, A. (2017). Effect Of Barbell Weight On The Structure Of The Flat Bench Press. The Journal of Strength & Conditioning Research.