Ahh. 7x64...the cartridge that was once an idea for an ideal "sniper rifle" cartridge for the German Army. It and its belated American "clone" the 280 Remington are probably the two most versatile and useful cartridges out there in a standard Mauser length action.
I have a 280 Remington.
The huge advantage they both have over the 270 Winchester is that .003" diameter. Now on a paper target or on a deer there is no difference. But what that .003" does do is unlock access to the wonderful world of 7mm.
And as far as bullet selection goes that is a huge difference. 150 grain, 165 grain, 175 grain and, of course, all the exotic TIG and TUG and other continental bullets in that size. That's where the two really outdistance the 270 Winchester.
However if all you ever want to shoot is standard "cup and core" lead bullets around 140 grains or say 150 grains maximum than do you really need a 7x64 or a 280 Remington when 270 Winchester (in that bullet weight range) is adequate.
I like 280 Remington (the standard version) and woukd rate 7x64 similar yet if you don't need or want those exotic bullets or weights above 150 grains then 270 Winchester is maybe better?
BUT ON THE CONTINENT? Then no question of 7x64 being the choice with 270 Winchester a long way behind! And for you, as a reloader, it means that one size (.284") does truly fit all in your 7x64 and 7mm-08. Although if you have a 7mm-08 then why not consider the next up after 280 Remington and go direct to 7mm Remington Magnum?