advantages between green screen and forced prospective .

For the giant scene of my FMP i intend to film using two different techniques , such as forced prospective and green screen .
Green screen ...  I will film  the giant separately using the green screen and then super impose the footage on top of the character running in the background which will be filmed in the Royal Crescent.  The advantages of using green screen are that making the actions match up more accurately and  gives prospective more realism. A problem with green screen is that because you film each layer separately the lighting will become inconsistent . this is because natural light will  look different to artificial light .
Forced prospective is more difficult to film and requires more setting up .  it requires the actions between the actor and the foreground  to be in perfect unison . Focus is the difficult thing with forced prospective , keeping the area between the actors in the foreground and the actor in the back ground clear and in focus .