On my chronograph, all things equal, particularly barrel length the 9.3x64 out distances the 9.3x62 with a whole 150 FPS average...mostly in the 100 fps catagory...With a 300 or 320 gr. bullet that 150 FPS may or may not be substaintial..up to you to make that call.

Based on that I shoot the 9.3x62 these days, however the 9.3x64 is one hell of a cartridge and has proven itself with proper bullets as the most all around cartridge in the world...

Since it will feed and function in about any std. action then why not take advantage of its slightly more velocity, but I would not run down and trade off a good 9.3x62 for that...and I am not sure just how long that Hornegber brass will be available, the 9.3x64 seems to come and go and thats a shame, its a great round and needs a fair shake.