I have never had anything to do with the 7x57,I sure it is very good because it has been around for awhile.As 8mm/06 with the 7/08 you have a short action but because it a short action don't mean you cannot twek it up either,I was trying new loads in my 7/08 this past summer and got an average of 3120fps with a 130 gr bullet.
If it was me I would pick the 7x57 because I don't have one,but I think you will like either one.

http://www.hunting-pictures.com/memb...ght&encore.jpg