The sole advantage to VDO is that it allows you to advertise a lower rate.
This is lost the first time the hirer sits for 15 minutes at the holding point waiting for a break in traffic to take off and works out they spent $70+ to just sit and watch aircraft.
That is a BIG disincentive to coming back and doing it again. I would much rather pay a higher rate for air time, and not have the dollars ticking over while waiting on the ground. Especially if the operators costs are primarily based on airswitch.