Charlie, after doing some reading, what you called a primitive system appears to actually be fairly advanced. Although the seperate lift fan is dead weight when not in V/STOL mode, it's employment allows it to be able to go supersonic, which the Harrier cannot.
Which is a shame that the Harrier wasn't allowed to be developed into a supersonic aircraft. Had the P.1154 seen the light of day then maybe Harrier II would have been a little different. Being supersonic isn't everything either. In peacetime its a nuisance, and really, for the roles it is taking in
British service, not really important. That's not the US' problem though!
It also allows the F35 to take off with a greater payload than the Harrier, and it's scheme allows for cooler air to hit the pavement which reduces wear and tear on the pavement.
Fair point. Really depends on the eventual operation. Whichever way, in the
critical (mission wise$) phase of flight, it is a fairly dead weight.