A quick tip on making the most money in the career is to do most quick races on the easiset settings and progress your way upwards along the difficulty skills. This gets you over $100k for every race and is quite rewarding in the end. Overall on one race I made almost 1 million after doing the same quick race on all 5 levels of difficulty. 
In regards to PC vs X360 versions. I had played the demo on both platforms and selected the X360 version simply coz my 8600GTS couldnt keep up in the frame rate department.
In regards to PC vs X360 versions. I had played the demo on both platforms and selected the X360 version simply coz my 8600GTS couldnt keep up in the frame rate department.