I think one of the major benefits of going from VNAV to FLCH is speed control, on the 7576's speed control in VNAV is not as accurate as FLCH.FLCH will give you idle throttle in descent and Climb power in the climb, VNAV will vary during descent in order to make any restriction you have entered in the FMC. I generally switch from VNAV to FLCH at 10000' as the default setting on the FMC's (for our birds anyway) is 240 kts. So I'll switch to FLCH to maintain 250kts and not screw up the traffic flow into the airport. Thats my 2 cents worth....