The 450 No2 and the 475 No2 are not the same cases.
The 475 No2 has a bigger base and a larger diameter rim.

Before I bought my double rifles I thought of all the Nitro Express rounds I would like the 450 No2 the best.

First the 458 Bore, the choice in bullet selection alone is reason enough to get any variety of 450 Nitro.

The No2 case has a thick strong rim. It has a definate neck, which is a little easier to load then a normal straight sided case.
Also since the case body is larger that the bullet diameter it is very easy when reloading the rifle, as the bullet is much smaller than the rear diameter of the chamber, so you are inserting the .458 bullet into a .56 diameter hole.
After nine years of shooting my 450 No2 on the deer lease, and one trip to Africa [3 elephants and 2 buff], I feel I made the right choice, for me anyway.

I also have a 450/400 3 1/4" and like it very much.
In reality all of the Nitro Express cartridges will get the job done, I just like the 458 Bore.

I shoot quite a few 350 grain Hornady RN bullets on deer and pigs.