I used to think the newmatic style are more reliable without a bail to break, but I've realized they are somewhat depending on the strap being tight to stay on. The straps always seem to loosen up throughout the day, especially when trudging through snow, and are one more thing to catch a point on. I'm just curious what you guys prefer for multi day mountaineering trips? For reference, I'm using G12s with Baruntses so I get a great fit with either system.
In Peru I used Baruntses with automatic BD cyborgs, never had a problem with them. I've used newmatic/strap ons for snow/alpine ice and by the end of the day they're usually a little loose, especially if the straps are wet.