The IB is calculated out of a score of 45. You do six subjects where you must do at least three of those subjects classed as 'High Level (HL)' and the remaining 'Standard Level (SL)'. HL classes can sometimes be classed as the equivalent to some first year uni classes, meaning you can do the second year of it at uni. CAS, (Creation, Action, Service) is a compulsory community service program which is vital to complete in order to pass the IB. Without doing the required 150 hours (50 hours to each of the three parts), you will not receive your diploma, even if you have aced all of your subjects. Your CAS is also three points towards the total of 45, as 6x7=42 and the remaining three are from completing CAS.
In the IB you cannot play to your strengths. You do one subject from each area, so one 1st language, one maths, one 2nd language, one humanities, one science and one extra subject from either humanities or science. This in turn makes it harder to achieve a higher ENTER score.
The IB is a diploma that lasts a lifetime, unlike the VCE where a one's ENTER is credited for a maximum of two years. By completing the IB, you can also apply to any university in the world, however whenever applying for college's in America, the SAT is still compulsory to sit.