In response to BEagles problem, think the GS with whizz wheel is 100kts and with the MDR method is 103kts. On a 40nm leg would be 30s difference in timing for example.
Of course, all this is based on forecast winds - think that is another thread in itself! It'd be interesting to see what people use for planning winds - I tend to use the spot forecast, but also have a look at METARS of airfields along the way and approximate the 2000ft wind to just check there is no wacky differences around.