LO,
The B has LOTS more wing (about 3X) and a lot more flap, as well as a Leading Edge device. It can also use all its control surfaces to get maximum lift at desired speeds, thanks to its integrated control system. (on a Harrier, integration of wing lift, propulsive thrust and attitude is done via pilot skill).
PBA,
If the aircraft lands in a semi jet-borne mode, the propulsion system should already be spooled up - in any case, response of the system has to be fast to provide the vertical hover control required. Don't forget that the Harrier's Pegasus was, for many years, the biggest and most powerful dry engine in any military aircraft, and also has the fastest throttle response - due to brilliant british engineers....same breed of guys now working on JSF.
Best Regards as ever,
Engines