The new rangefinders are amazingly small and sophisticated with good optics at the high end. But you aren't going to see a huge difference in performance from your old Leica. I bought the CRF 1000r last year for elk hunting in CO and am very pleased with it for my uses including archery. But if I had chosen the Zeiss or the Vortex I think they would be perfectly capable.
My decision to replace my trusty Nikon 800 was because I looked through a Leupold 1000 in foggy conditions and it worked where mine failed.
