Having built rifles for both cartridges and hunted with both, I found no realistic difference between the two cartridges. Neither were improved originally. If you need the best brass, RWS is in stock at Huntingtons.
I prefer the 7x64 Brenneke because I have an original Guild rifle chambered for this cartridge. It's one of the very few rifles I can still use with the original iron sights accurately. The twist won't allow for the heavier, longer VLD bullets but even the factory Norma ammunition (discontinued) is accurate. I bought several boxes on closeout prices.
Enjoy!