Improved versions? Kind of like asking guys whether they prefer blondes, brunettes, or redheads...you'll always get a myriad of responses, mostly based on personal experience. In my humble 45+ years of experience the venerable (unimproved) .375 H &H has done it all, splendidly. Duiker to Buff, and any and all in between. Elk, Red Deer, the Big Bears ... you name it.
Inside 300 yds ( which is considered gentlemanly in my circle ...with the exception of Buff, Elephant, Lion, and Leopard) one could not do better.
With (I believe) 14 fine rifles in all flavors to choose from, my LH Chet Brown Pro Hunter in .375 has travelled 3-4 times the miles of the next 4 combined through the years.
An old man...not looking for a cat fight...just sayin'.
Cheers
Spike