OP is in Brasil - CFDs and options have been available both OTC and exchange-traded. The ASX briefly listed CFDs to remain competitive with its option listings, although they eventually delisted the CFD's. As has been mentioned they are not currently allowed for retail investors in the US market. One factor that has made CFD's attractive is that in many places where they are offered they can be bought on margin(options in the US aren't marginable and don't generate any SMA - but they can REDUCE THE SMA requirement if they are bought as a hedge in a portfolio margin account). Generally where CFDs have developed a following a good deal of the demand has come from the desire to gain additional leverage or simply to avoid listed option requirements and suitability. Additionally, where they have been made available they have often had a material marketing budget with the OTC dealers investing heavily to develop a market. There are a handful of other differences especially with the way the borrow/lend is handled.
To your original question - in most markets, it's the leverage difference.