This is a very fair question
BeeMaa. I asked myself this question seriously before I committed to the .257 Wby.
The answer that I came with was: .25-06: 100 gr TTSX @ 3,200 fps and .257 Wby: 100 gr TTSX @ 3,600 fps.
While the 100 fps difference between .280 140 gr and 7 mm Rem Mag 140 gr can be mitigated by individual loads and rifles, I reckon that the 400 fps difference between .25-06 100 gr and .257 Wby 100 gr is substantially meaningful
However, is there anything the .257 Wby can do that the .25-06 cannot do? Absolutely not! But I personally liked the additional 30 yards of MPBR.
Truth be told, does it still matter as much today as it did yesterday?
I suspect that the answer is no. An accurate custom calibrated BDC (bullet drop compensation) turret for a specific load in a specific rifle, validated by actual chronographing of the load and actual shooting at the actual distances 100, 200, 300, 400 yd, and that only takes rotating
without further thinking to 175, 250 or 325 (for example) after an accurate EHR (equivalent horizontal range) reading from a reliable range finder, makes flatter trajectories likely obsolete...
This, by the way, is the only reason why the 6.5 Creedmoor, which is quite slow and has rainbow ballistics, was able to transition from the paper punching fields to the hunting fields, although most hunting rifles are still adorned with MIL or MOA turrets that are - in my view - poorly adapted to dynamic hunting...
I will test a custom BDC turret in Africa on the Tiny Ten in September 2020 (hopefully!) or 2021, but I suspect that laser range finding technology and custom turret engraving of an individual iPhone ballistic app chart, have changed the game...
I resisted adjustable MIL or MOA turrets while hunting (although I use them to shoot steel at 1,000 yd) as long as they involved reading the dope chart to convert the distance to MIL or MOA correction, counting carefully the 27 or 43 clicks (for example) required, and not having an instant visual check of whether the turret is where it should be. This simply did not work in a dynamic setting. However, the direct engraving of actual distances on a custom turret calibrated to a load and a rifle has me tempted. I KNOW that the concept works, I used it on the FRF1 French sniper rifle in the early 1980's and it was deadly...
This being said, for new hunters forget about all that. Sight a decently flat shooting non-magnum caliber for its MPBR and keep their shots under 250 yd until they have proven they can shoot farther...