RE: 375 RUM OR 375 H & H?
Have never shot the 375 RUM but I have both a 378 weatherby and a 375 h&h.
The 375 h &h is a great all around thumper and the kick is mild enough not to have a break. I like it alot.
The 378 weatherby on the other hand will do it all even long range shooting. But you will have to have a break. Like EKM said it would be the top of the 375 food chain.