Ive owned a pair of Leica 10 x 42 BRF’s for many years. Originally purchased them to get down to a single instrument for glassing and rangefinding. While the glass is still excellent, their range finding performance has dropped off dramatically over the years, in spite of returning them to Leica for service and recollimation. Two years ago, Upon upgrading from Kestrel 4500’s to a Kestrel 5700 Elite with Link, I was in the same boat as you… Trying to choose the best Range-finding option to employ with the 5700. At the time, the Leica 3200 Binocular Rangefinders were just coming out and my desire was to stay with a single instrument for rangefinding and glassing. Problem at the time was that the 3200’s were getting poor reviews for connectivity with the 5700‘s. To limit financial exposure, I choose to go with the Leica 3500 Monocular Rangefinder. Although I’m back to carrying two instruments again, the 3500’s have served me well. They are light, compact, range exceedingly well, have excellent glass (only 7x though), and connect well with the 5700 when you abide by few rules (Use Lithium Batteries in both Units, keep the Kestrel in front of and above the 3500’s). My experience only; Your results may vary.
Regards
JHC