It does have to be agreed, they are rather beastly!
Cavani, for me personally, is the more complete player of the two however.
Cavani reminds me of Chelsea's Drogba in his prime - A work horse who will help at every set piece, run all over the pitch, and be a dominant/scary force vs. the opposition.
Falcao feels more like...everything Chamakh of Arsenal dreams of being. He doesn't help his team much, doesn't have a great work rate, BUT, will score you goals regardless of who he's playing with or who you're against.
So basically - I want us to sign Chamakh. (Bad joke, I know.)