If I were you I would use the G25 so you can get the feel of it on the other tracks even if they change when GT5 comes out.
Try this for your G25 wheel with your PS3 and GT4:
Buttons for the G25 wheel and PS3
Top 4 The Black ones
Top-triangle-cancel-reverse(gear to back car up)
Left-square-cancel
Right-circle-E_brake
Bottom-X-enter You can also use the gas pedal for enter
Bottom 4 buttons The Red ones
Far left-no function
Second button-Change view
Third button-Pause-quick exit replay at the end of race-This button will also speed up the winnings (to keep from waiting with the cup spinning around so you can get back to racing)
Fourth button-best race line for license test
Buttons on wheel
Left-look back (default)
Right-nitro (default)
I change these two buttons around myself so I have the nitro on the left.
D-pad-same as the controller up,down,left,right. For menue use.
Also for (during race)
Look back-bottom pad
Look left-left pad
Look right-right pad
To change any of the button functions use the DFP settings in the options menue.
I have not used the wheel in photo mode. The only thing you can't do with the wheel is "exit" game. I also never have my controller on during gameplay I only turn it on to exit the game. If anyone needs anymore help with this wheel give me a shout-back and I'll try my best to help.
One last thing make sure your wheel is in the far left port(port 1) or port 3
Hope this is helpful,
opelgt
Try these settings for your G25/PS3 and GT5P:
Try using these buttons for your G25 wheel on your PS3 for GT5P: