Thanks everybody
Is it possible to understand that in LVL CHNG the thrust is CLB/-1/-2 for climbs and Idle for descent, pitch is controlling the speed as selected in the MCP. However, in V/S mode the pitch controls the V/S and thrust tries to maintain MCP speed as far as possible.
So Lvl Chng should be the mode providing more exact control than V/S through, large magnitude of descents. Can someone dwell upon the reversions, we had a case of one pilot descending in V/S and exceeding the Vmo in the B737NG.