The 6.5x57R gets my vote. Cases can be readily formed from .444 Marlin brass for those who are economy minded.

Years ago I had a custom Win. Highwall built as a varminter and chambered for the .257 Roberts rimmed. At that time rimmed European brass, such as 7x57R and 8x57R were hard to come by. I made my brass from .444 Marlin. It's great for such. I'm currently making my 9x57R from the same brass.

The .444 can be troublesome in the 8x57R because the 8mm has a thinner flange. Some will take the .444 and some won't.

Curl