Recommended handlebar style for short daily commute? I am looking to buy a bicycle for a San Francisco city commute totalling 4.1 miles (about 6.6km) in each direction.

My question is, what handlebar position (and riding position) would be recommended for such a ride?

I notice drop bars are very popular here, but I am concerned that the bent over position would be stressful given that I will be commuting 5 days per week. At the same time, I do not want to overly stress my quads. Perhaps a compromise is recommended?
For a short commute in street clothes I opted for flat bars with bar end extentions. This allows some different hand positions and for me a more comfortable upright position. If you are riding for the first time is several years, bike fit is more  critical than bar type. A bike that is the wrong size will never be comfortable no matter what type bar it has.