I own or have owned pretty much every 375 except the Ruger.
Hard to argue with the H&H being the best choice in terms of rifle selection, ammunition availability, historic relevance, and that it feeds very well.
If you have never owned a 375 this is the place to start.
My second choice is the modernized H&H... the 375 Weatherby.
It is easier to load for (burns almost any reasonable powder and is accurate with almost any amount) and has a bit more giddy up for heavy bullets. If you can shoot the H&H you can shoot the Weatherby.
In third place is the 375 Ultra.
Though it is my personal favorite some guys will not like the extra recoil (especially in the light factory Remingtons).
The extra horsepower the Ultra offers to a heavy bullet shooter is impressive and I would go so far as to say that in the right hands it is the ultimate long range moose/elk/buffalo/whatever rig.
The smartly driven 300gr Barnes absolutely hammers game....Enough so that I got rid of my 416s.
The 375 Ruger would be something to buy if you really like the little Ruger rifle....I see no other reason.