I would avoid any belted magnum that doesn't rely upon the belt. For many years the .375 H&H was the parent cartridge for necked down magnums, though these calibers had more than enough shoulder to headspace there. The reason why the WSM series used .404 Jeffrey dimensions was to claw back some case capacity from space which is dedicated to the belt in the older magnums, and in fact used a rebated rim so that it could maintain commonality with the standard magnum .375 H&H bolt face.
This only becomes an issue if you reload. If you choose not to reload, then two things happen: 1) the belted magnums are indistinguishable from non-belted magnums and 2) the price of ammo is and will be a limiting factor for practice with that rifle. For many years, I advised people that you handload for performance, and that you will never save money reloading. That's no longer good advice for high power rifle rounds, magnums in particular and Africa calibers most of all. .458 DGS 500 gr bullets are $1.30-$1.80 each, but .458 WM ammo is $150/box ON SALE for DGX bullets that most folks on here aren't fond of. 7mm and .300 magnums are better, but you can easily pay $40-70 for a box of 20 rounds while 190 and 250 gr ATIPs are $0.95/bullet. and $0.35 for the rest of the stuff (i.e. Fed 215M/H4831SC and Norma or Hornady brass with 4-6 firings per case). Reloading is a big deal now if you really want to get practice in and aren't a gajillionaire.
This matters because addressing headspace on a belted round is a tedious and specialized skill where the fund of knowledge available means that you will ruin a bunch of cases using proprietary tools to get more than 3 firings out of a case. Despite the cost and unavailability of .458 WM cases, I made the decision to toss them when they stretch too much (granted that's not a case where the issue arises very quickly vs. necked down magnums which suffer more quickly). It is a problem that can be addressed, BUT there is no reason to buy a new gun with a cosmetic belt in the modern age when you can buy a caliber of equal performance which does not require that effort or expense. The belted magnums are a cool part of history, and I have fond memories of shooting a buddy's 7mm RM Mark V, but there is no difference between a belt and one of those multicolored LED lights that every OEM sticks on computer parts these days.