RE: 6.5x55 vs. 7x57
I also own a rifle in each of these cartridges. I actually own five different 6.5 X 55's...but only 2 of them are good sporters while the others are military configuration. My 6.5 X 55 sporters are wonderful deer rifles, while my 7 X 57 is also a wonderful deer rifle.
I would be hard pressed to choose between the 2 cartridges since I consider them to be among the best of all the "deer" cartridges while possessing a versitility that can span far above and below the size of deer. Woodchucks to moose/elk with maybe even some decent sized black bears thrown in would be easiliy handled by both of these fine cartridges.
You can't make me choose.
Both will be maximised by handloading.