There is no question that with conventional 25 cal bullets the options are pretty limited as far as comparing them to the 7mm family of bullets.
That said, there are bullets out there that turn the STW into a totally different critter then it is when used with commercial bullets. Why the industry has not pulled their head out and changed the standard twist rate for the 25 cals from 1-10 to 1-9 is it is with most 6.5mm chamberings.
With a 1-9 twist, you can shoot custom bullets up to 142 grains in the STW. There are not alot of them out there but they are there. The huge 156 gr ULD RBBT from wildcat bullet is an amazing bullet. The 257 STW is the min chambering I recommend for this bullet as you will only see around 3100 fps max with a 28" barrel but when you consider your driving a bullet with a BC in the 0.8 range, it takes this chambering into an entirely different long range performance class. The sectional density of this bullet is also extreme. Still, the rifle must be designed specifically for this bullet and that will eliminate some other bullet options such as most conventional jacketed bullets will not handle the 1-8 twist needed for these bullets. Still all ballistic tips and accubonds would work fine as would all X or TSX bullets.
For something a bit more conventional with a 1-10 twist barrel, there are 125 gr and 130 gr custom bullets out there that will do ANYTHING that a 140 or 150 gr 7mm bullet will do and do so at the same velocity.
BCs are basically identical to the 7mm bullets. Muzzle velocity is a bit more for the 257 but barrel life is shorter for sure.
Again, with conventional commerical bullets, the 257 family is lacking badly but there are other options out there to provide us better results and will allow the 1/4 bore magnums to act much more like 7mm magnums they they really should.
Anyway, the STW is not WAY overbored, my 257 Allen Magnum is WAY overbored!!!