Help needed with the Dragon!!

Both moves are strong, I play the dragon as black and the yugoslav attack against it as white so i play Bc4.

 The main difference is that against o-o-o almost all strong players will play ...d5! breaking in the centre, with an equal game the only problem with this line is that black gets lots of play and white can generally forget about the 'sac sac mate' on the h-file.

After Bc4 black will play Bd7 followed by Rc8 then Ne5-c4 white will proceed with Bb3 ,o-o-o and then throw his h-pawn up the board. With Bc4 you prevent ...d5! and the position will be more dynamic with winning chances for both sides. I recommend buying a book on the dragon, depending on your ability either get 'Starting out the sicilian dragon' by Andrew Martin or the more advanced book 'Play the sicilian dragon' by Edward Dearing 

maybe play it through a computer or look it up a book?

How is black doing in the main line yugoslav?

in first diagram 0-0 is played. Nc6 is only played after Qd2

in second diagram Bc4 is played because like fm_holland said, d5 can be troublesome. however, if white is a good defender, then 0-0-0 should just leave white with a better position (and in the case of a ...d5 break, an extra pawn).

Then why do people play 9.. d5 is black is going to be down a clear pawn? Is Nxd4 a good option as well, distracting white's bishop from Bh6?

according to chessgames, after 7...0-0  black is winning 23.6% white is winning 46% and draws are 30.4%

Bc4 seems to be doing slightly better than 0-0 with 29.1% wins compared to 22.2% wins and there are less draws.

why did you delete your comment? I thought that some of the info on "that site" was very interesting and insightful

woops no advertising.. sorry :I