The best of the 7mm calibres is undoubtedly the .30-06 or the 8x57.
However as you specify 7mm the options are 7x57, 7x64 form the continent or 7mm-08, .280 Remington, 7mm Remington Magnum from the USA.
Of the five the last, 7mm Rem Mag has a belt and this means one less in the magazine and sometimes "issues" with feeding. In real world terms it doesn't offer much up to two or three hundred yards that the others do. Over three hundred yards it offers the advantage of a higher initial velocity.
7x57 is moribund. Nice cartridge, nothing wrong with it. Will do anything that you want but on the continent it was never in everyday use in France where the 7x64, 7mm-08, and .280 Remington (in that order) were popular. 7mm Rem Mag in both France and Germany seems "passed over" as most go dierct to the .300 Rem Mag.
My choice would, as I say, be .30-06 but if you want an all around flexible 7mm then 7x64 is the way to go. In the USA then ,280 Remington. I have a .280 Remington and a 7x64 but here in UK the .280 Remington it is a niche cartridge, a pity, but that is reality here in UK.
And as .30-06 is now legal in France I've put my 7x64 up for sale. See below. Currently at Holt's but will be collected by me in the New Year and available for offers around what I paid for it....£ 3,250.
If you've £ 3,000 to £ 4,000 to play with than look here.
View attachment 64596
http://auctions.holtsauctioneers.co...alelot=XA1215++1109+&refno=+++94747&saletype=