The reason for biodiesel is that it requires no modification of the fuel line, veggie oil needs to be preheated in the tank to become nice and viscous, and also needs a switchable valve to cut the flow of diesel and open the flow of veggie oil to the engine. Generally, biodiesel is better for non-nomads, since the kit is separate from the vehicle and for smaller vehicles, that frees up space and keeps the weight a little lower. Something like a large bus should have a veggie oil system, since the lower miles per gallon and larger fuel tank would mean that the labor for the biodiesel would be much greater, and the weight and the space the system would take would not be significant.