There IS no 'magic bullet' when it comes to sprocket size in a single gear ration system. It is a compromise between acceleration and top speed. The factors that come into play are the riders weight and the terrain, as well as what is more important to the rider.
As others have said, the smaller the rear sprocket, the higher the top-end speed. However, the smaller the rear sprocket, the lower the torque applied to the rear wheel, (and thus the lower the acceleration.) If the terrain is flat, and you're a low-mass rider, then the 44 tooth sprocket will give you a high top end with acceptable acceleration. If you're like me (a rider whose scales groan at sight of him- I was a defensive tackle in college, after all) or who will be riding in the hills a lot, you might want to go with the larger sprocket.