The .470 has stood the test of time as the most prevalent rimmed DG cartridge for a reason. In a DR it offers the best combination of rifle weight/recoil/stopping power/penetration. The standard by which all the others are judged.

No one has ever really needed to tinker with the conventional load: the 500 gr bullet at 2150 FPS. Good factory ammunition is readily available.

Anything bigger is overkill. You will shoot better if not fatigued from carrying a heavier howitzer all day, and shot placement is far more important than a marginal increase in caliber. Additionally, your second shot (if necessary) will be a bit better/quicker if you have not been punished by the recoil of your first.

You can go a little smaller/lighter (back to the various venerable .450's), but why bother when you can use what superceded them, making the best, low pressure use of the earlier .500's case?

As Craig Boddington has written it is a .470NE world, and that is a very good world to live in...

Fine, use something a little different, but you won't find anything better.