I actually play sambo quite a bit, and I very much prefer knee reaping over the 50/50. If I'm sparring with a guy that is at least familiar with the 50/50, then it often ends in stalling, and my ankles are still somewhat at risk. My best options in the 50/50, in my estimation, are to roll over onto my stomach and attempt a belly-down ankle lock, or stand up and smash them, then pull my leg out.
With knee reaping, I feel much safer, and the control there is just amazing, meaning that I have superior control. In the 50/50, you have control as well, but so does your opponent. I also really like working the sambo-style straight ankle locks, and knee reaping is a good setup for that. The compression-type straight ankle locks from jiu-jitsu aren't nearly as effective, and I can usually catch BJJ guys there because they're used to sitting ankle locks out.
With knee reaping, I feel much safer, and the control there is just amazing, meaning that I have superior control. In the 50/50, you have control as well, but so does your opponent. I also really like working the sambo-style straight ankle locks, and knee reaping is a good setup for that. The compression-type straight ankle locks from jiu-jitsu aren't nearly as effective, and I can usually catch BJJ guys there because they're used to sitting ankle locks out.