The 9.3x64 is pretty close to a 358 norma mag, the 9.3x62 is right there next to a 35 whelen. I've shot alot of bears with my 9.3x57 and quite a few with a 9.3x62. The few I managed with the 375h&h where sure a little more dead and seemed to flaten them black bears a little faster and flatter.

I like the no belt of the 9.3x64 but the 9.3x64 has less taper so I'd say feeding works out pretty close.

Ammo availability is better with the 375hh by a large margin. Ultamitly I'd go for a new 375, but you can some times find a great used mauser in 9.3x64 for a steal compared to a 375hh.