"yotenaylor" has a good point about lack of bullet selection but that's true of every caliber except 30 caliber. Oops---that puts "nitis" back with a 30-06.
According to one chart, the 257 Wby has a case capacity of 85 gr and the 25-06 has a capacity of 65gr. Using Hodgdon's site that gives the Weatherby a whole 290 fps over the 25-06 with a 100gr bullet.
But compared to the 243s and 22s, the real value of the 257 is that it shoots heavier bullets, up to 120 gr., with almost the same ballistics. So more weight gives you less wind drift and more terminal energy when compared to other bullets, but then again you just burnt more powder.