I haven't used a Keyence but between the VFS and Tekin speedos I would say the Tekin is defiantly better.
Compared to a VFS-1 my tekin ran cooler, was smoother with more punch, did not require a cap to keep my servo running strong and was much faster and easier to program.
The tekin does have a larger footprint and should be more difficult to locate but it is also looks much more robust and should a failure occur their repair service is much faster.
Mark