I've got extensive experience with both brands, including disassembly and minor mods. I haven't seen any real difference in overall fit or finish. Both seem to use the same ceramic bearings captured in a brass cage. The liners and scale materials seem to be the same. I don't have experience with the Sachse but my other Sencut knives have the same level of liner skeletonization as the Civivi knives. The screws seem to be the same but...
A major difference is that Civivi pivots are captured via a tab underneath the logo. Because the Sencut knives do not use the logo piece, they are free-spinning. I get it but I really wish they would have just gone with a D-shape or something. Honestly, this has not been a problem for me on models with wood or Micarta scales. There is enough friction to seat them. However, their steel frame lock was steel on steel in a place where oil could migrate. Getting it finely tuned was kind of a pain.
There is a difference in steel but you've got to take it for what it's worth. I don't have much experience with their Nitro-V and haven't seen any testing. However, Civivi and Sencut both seem to use the same 9Cr18Mov with the same outstanding heat treatment. That's already a reasonable budget steel but WE takes it to the next level. I'd take it over Spyderco's VG-10 on edge retention and the corrosion resistance is better too.