I've hunted quite a bit with both the .243 and .250, and so far haven't seen any difference in the way they kill deer and pronghorn.
I was thinking the other poster may have had a long range situation in mind where a fast twist 6mm and a long sleek bullet could have some advantage in the wind.
For my purposes, when I've been out with my 250 shooting 100 grain Ballistic Tips or Interlocks at 2950 fps I don't recall thinking "I wish I had my 243 right now". Of course, when I was out with my 243 I didn't pine for my 250 either.
