I think your level of fitness is more important than riding position or wind resistance in regards to speed, unless you are solely a speed oriented rider riding full out road bike with drop bars. I've tried bikes with drop down bars. I actually have an older one. I can't make them work for me. At 55 years old, I need a more upright position and I simply need to work around any other issues. I ride my bikes for exercise and to be outside. The more comfortable I am the more I ride and the more exercise I get.

I could see where in a highly unique set of circumstances a fixie could be faster but for the vast majority of riders in the widest range of riding situations, I do not agree that a fixie would be faster.