I think the .375 Ruger is great from what I read, but I think it's doomed to fail when going up against the .375H&H.
The .416 Ruger however has a chance in the .416 arena, and may go on to help out the .375ruger, but amongst the .416's, none of which are really popular, I think a .458win mag and lott are probably more popular than any .416...
You've got the huge .416 rigby, which I read recently but prior to the introduction of the .416ruger, that the riby was the only one that the author thought would be around in 20years or so...
If going with a .375, it's the H&H hand downs IMO.
If it's a .416, it would be either the Rigby or Ruger.
The .45/70 certainly can get the job done...
You certainly don't need a .416 for brown bears, the standards are the .338 and .375
It's impossible to go wrong with the .375H&H or .416rigby, but in 20years you might be kicking yourself with a 375 or 416ruger...