Are you going to hunt with it? Back in February you asked opinions between a .470 and .500.
Now, it is .500, .577 or a .600?
All of the guns, if you buy from a reputable manufacturer will be accurate enough (regulated to 2" @50 meters). So, accuracy and handling will be up to you.
As you go up in caliber the weight of the gun will be going up. My .500 weighs 11.6 pounds, .577 will weigh in at 12.5 and I think most .600s are 14 pounds and up. Cost of the rifles scale up with the caliber as well for the most part.
In regards to stopping power assuming correct shot placement all of them will have the stopping power. Penetration is more dependent on the bullet than the caliber (to a certain extent), not that many selections for .600.
Personally, of the three, I'd go with the .500 NE for the reasons you mentioned. However, as people mentioned in the thread from February I'd go with the .470 NE for your purposes.