It appears we can not in any scientific terms choose a clear winner, so one must look at other variables.

Based purely on mathematics the 600NE has an energy and section density advantage.

The 577NE an ease of use advantage based on the lighter weight (which some of you preferred) and less recoil.

Both achieve greater than 7000 foot pounds of energy which is massive by any standard.

I believe reloading the 577NE to be cheaper, brass and bullets easier to come by, although still expensive compared to .458 cartridges.

Stopping power, as defined by many to be the ability of a gun to stop a charge either by turning or killing of the animal. This is difficult if not impossible to quantify IMHO. Both have enough energy down range to kill anything on this planet, with some to spare I would venture. I have little faith in TKO numbers, but if one believes in these, the 600NE is the leader.

So based on the math, the 600NE should have the advantage in killing/terminal ballistics. The 577 in ease of use and cost. But does the ease of use then give an advantage in killing/terminal ballistics?

Like I said no clear winner. So I base my choice on ease of use and pick the 577NE, IMHO.

Of course we are leaving out of the discussion many other cartridges that produce far more energy than either of these, however, they are neither main stream, nor, IMO, practical in the field.