Just my honest opinion so far. Add your own..
Physics - GT5, definitely!. The difference between each engine/drive layout (eg FR/MR/4WD etc.) Is very well implemented in GT5. Forza doesn't seem to grasp the MR/RR layouts so well (try 'lifting off' mid corner in either and you'll notice the difference. (I have owned FF/FR and MR cars in real life, so believe I have some say in this area..?)
Sounds - Forza 4 (by a massive margin!)
Graphics - GT5
Career mode - Hmm not sure. GT4 was probably stronger than both..
Online - Too early to say as I've not had enough experience of GT5 v2.0 or Forza 4
Game Menus - GT5 is a lot simpler and easier to work through IMO
Addictiveness - I still desire GT5 even if I do lust after the sounds of Forza!
Physics - GT5, definitely!. The difference between each engine/drive layout (eg FR/MR/4WD etc.) Is very well implemented in GT5. Forza doesn't seem to grasp the MR/RR layouts so well (try 'lifting off' mid corner in either and you'll notice the difference. (I have owned FF/FR and MR cars in real life, so believe I have some say in this area..?)
Sounds - Forza 4 (by a massive margin!)
Graphics - GT5
Career mode - Hmm not sure. GT4 was probably stronger than both..
Online - Too early to say as I've not had enough experience of GT5 v2.0 or Forza 4
Game Menus - GT5 is a lot simpler and easier to work through IMO
Addictiveness - I still desire GT5 even if I do lust after the sounds of Forza!