Having discussed this question at length several times and consulted the experts who run the hyperbaric chambers, the crucial issue is time to treatment. If you have a choice between a protracted low level transit and a quicker but higher level one, then the quicker option is the one to choose.
The sooner the casualty can be recompressed and given oxygen therapy the better the prognosis. I know it seems to fly in the face of common sense but that is what the experts recommend and by taking a long time to get the cas to hospital you can worsen, rather than improve, the situation.