Re: 7-300 Weatherby
Between the two, I would go STW because dies are there and the straight shoulder will keep stretching down better. Also, since not a wildcat, easier resale and reaming.
I had a 300Wby and was not impressed by the shoulder. Cases stretched more then I would have expected. I always neck size my brass when possible so that is not the reason.
Enjoy a great barrel burner.
PS, if just going to 1000yds, you may want to look at the RSAUM or WSM. With a 26" barrel, the can easily get 162/168gr bullets out at 3000fps. Plenty for that type of ranges.
The extra 100 to 200 with the larger case, may not be realized if the accuracy is not there. DC has used these for a bit so would have better hard data on barrel life and performance.