While logic can be a strong motivator, Emotion will win over it every time. Practical ballistics favors the 6.5x55, but It sounds to me like your heart is with the .257....
If it were me, I'd go with a medium bore. (8mm-.375) But then I'm a medium bore slut.
My best advice it to follow your heart. Go with the .257... In the long run, you'll be glad you did!
Grasshopper
"As you walk thru life, don't be surprised that there are fewer people that you encounter seeking truth than those seeking confirmation of what they already believe!"
Practical ballistics favors the 6.5x55, but It sounds to me like your heart is with the .257.... 