Yes, definitely no advantage going from open descent to V/S. As stated above, V/S can also be more difficult to manage because thrust is not at a fixed value in that mode.
Taking this a step further and assuming you are still in NAV mode and above the calculated vertical profile, changing from DES to OP DES will not change your descent rate either as both modes will be commanding Thrust Idle in that situation.
If you are way too high on the calculated profile and have limited use of the speed brake because of VLS margins, such as on the 321 when ATC have requested min clean speed, in my aircraft there is no shame in selecting flap early (below 20k and icing conditions permitting) which will reduce your VLS allowing for more speed brake extension. I always activate approach phase before selecting flap to prevent an embarrassing overspeed later in the arrival should managed speed be subsequently selected. Likewise there is no shame in retracting that flap later if unanticipated track miles have been added by ATC negating their continued use.
Alternatively, you could state your minimum clean speed is higher than GDot because you anticipate using speed brake to stay in touch of the calculated vertical profile, thereby handing the resulting separation management change back to ATC.
Either way, you have the opportunity to achieve a greater ROD than staying clean at GDot.