For what? Are you looking to complete the Formula GT Championship? If you are then don't buy either of the red ones in the new dealership but buy the one in the Online Car Dealership.
*troll* Well ACTUALLY the FGT isn't an F1 car, its a fantasy interpretation of an F1 car.
With payouts as high as they are, you should be able to do all of them. Get a Die, and roll. If its 1 or 2, get the FGT, if its 3 or 4, get the F2007, and if its 5 or 6, get the F10.