Physics is a good subject as it covers 200 marks and opting this subject gives you liberty of not choosing unfamiliar subjects like one from the Law portion, Urban Management etc. But it proves to be a very tricky subject because either you know something or not. You can write at least something about public policing or Waste Management etc but you can't write about Doppler effect just out of blue. So, if you have good knowledge and have academic background in Physics then do opt it. Otherwise it becomes difficult to retain Physics.
I consider that you can prepare 75% throughout the year and 25% on the exam night when you have to revise what you have prepared throughout the year. Thus if you feel that you have some other subject where you can score average marks by just studying along other important subjects then opt that.