I prefer old school myself, as far as 7x57 off the shelf ammo goes you'd likely be limited to Rem Corelokt or Winch Grey Box.
You could have a good gun shop bring in some Euro stuff for you. If you look around you could get some Sellier, Prvi or Norma.
This would be a good round to get into handloading is plan on shooting plenty, factory is readily available but handloading for this round is worthwhile unlike some others.
I have seen it written that the 7mm-08 is a hammer at 500 yards.
I have not seen anything as such about the 7x57.
I too, have both and love them both.
You need to be a handloader to get the best out of the 7x57. Mine gives the .270 a pretty good run for it's money. If you don't load your own, and aren't planning to, the 7-08 makes more sense, though to me it's kind of like recommending a Mazda Miata over a Porche 911 or Austin Healey.
Would that make the 7.62x39 a Yugo?
If you are a slave to the ammo manufacturers, then the 7mm-08. If you handload, then the 7X57 does all that the 7mm-08 does and more.
.....The 7mm08 comes out on top if you don't hand load, they are equal if you do......




























