I shot a lot with the 9,3x62 and the 375 H&H Mag
My experience is that the 9,3 x 62 With 286 grs bullett is a litle bit quicker and felt harder than the 375 H&H Mag with 300 grs. The 375 is a litle bit slower but heavy comaparing with 9,3x62
I use maximum load in both calibers.

They are both excellent caliber for big game hunting on the northern hemisphere. I know that the 9,3x62 can kill a buffalo, and some states in Africa has the 9,3 as theyr minimum caliber.