I have used them without and with lock valves. The lock valves are nice but kind of depends on how much the cylinder extends/drifts over time. I have a 3" gannon top link and the drift is minimal and it has no lock valve. I have a 2" and although not critical, is nicer to use with lock valve. I think it has to do with the size of the cylinder which makes one work better than the other. Most top link cylinders for CUTs are not 3" in diameter. The larger cylinders also move slower than the small cylinders.
The lock valve on the 2" cylinder will still drift over 24-48 hours. My large ag tractors have larger, 4-5" cylinders with internal lock valves and they don't move at all.