It is for penetation, some people think the SD of the.243 is a bit much for whittail and cosider the 80 to 90 gr better.
When one compares calibers one needs to compare bullets with the same SD. So comparing a 100 gr .25 to a 100 gr .24 is not the same, or a 150gr .308 to a 100 gr .243, etc etc etc.