My favorite lockback knife ultimately is the Recon 1. I don't currently own one. But if I were to keep and use a lockback knife, it's because I want the strongest possible lock that is still also convenient to use. For me, that has been the Tri-Ad back lock variant, and while the Recon 1 is imperfect in so many ways (unnecessary handle grooves, and a handle that forces the hand way back from the cutting edge, thick behind the edge, tip up only carry, thumb stud blade opening), these are issues I can solve by some modding, if desired. However, my lack of need for absolute strength in a folder has prevented me from going to whole nine yards on any of the Recon 1s I've owned. The change to an opening hole and tip down carry are involved enough mods that I don't want to take the time, and I've settled on the Spyderco Resilience with my own mods as my EDC folder.
TLDR: Recon 1, but I don't currently own or carry lock back knives.