Falcao is much better finisher, but Cavani offers much more to build up play, but I must admit I am not biggest fan of any of those two(even tough they are obviously excellent players), I would never swap RvP for them.
IMO, Falcao's style of play is identical to our Hernandez's, neither of them is excellent in build up, and both like to run behind the defence.
Of course, Falcao is better player, has better technique and ball control, but I really wouldn't bet on Falcao outscoring Chicharito here. Actually, it's interesting comparing their statistics even this season:
Falcao:
Scores every 99 minutes, goal+assist every 92 minutes.
Hernandez:
Scores every 123 minutes, goal+assist every 85 mins.
And if you exclude 8(!!) penalties from Falcao, Chicharito statisticly beats him in everything.
Of course, that doesn't mean anything, but I just wanted to point out how similar type of player we already have.