geography is a good all round subject that bridge the sciences and the arts due to the physical and human side of the course. It is good in straight geography, ecology side of biology, but also in politics, economics, management, law, education.
Both physics and geography are well respected, but physics probably opens up more doors in the engineering, mathsy, science department and compliments well with maths and is a great subject in its own right but from my experience geography is 'good value for money', its straightforward, esp. at AS.