>>76503305 (OP)
You need to maximize the overall weight moved if you are into bodybuilding.
Let’s say you can bench press 70 kg for 3×10 reps and 80 kg for 3×6 reps.
70x3x10 = 2100 kg total weight moved
80x3x6 = 1,440 kg total weight moved
By increasing the weight and decreasing reps, you reduce the total volume by about 40%, which means fewer microtears and less muscle growth.
On the other hand, if you are into powerlifting, then the opposite applies: you need to maximize weight and minimize the reps while not injuring yourself.