One of the benefits of the 458WM is that I believe it can be built as per a sporter weight 30/06 and still be manageable, particularly if 350gr and 400gr projectiles are planned. The 510's bite a bit more but it wont be noticed in the field. As mentioned before, stock design is super important. At one time I owned both a CZ550 in 458Lott and Marlin 45/70 ... with both loaded hot the CZ was by far the more comfortable of the two rifles!
Cheers...
Con