Why certain objects reflect while some refract? Both reflection and refraction are processes where absorption and re-emission of electromagnetic waves occur, but they differ in the direction of re-emission. What factor particularly decides the direction of re-emission?
 A: First, some objects do both reflection and refraction. 
Refraction is when light gets deflected when passing through the interface between two mediums of varying density. This happens with glass or air or water too. In this case the wavefront enters the new medium.
Now reflection is the change of direction of the wavefront at the interface between two mediums, when the angle changes in the opposite direction or close to that. In this case the wavefront does not enter the new medium.
Both cases are more elastic scattering. Where you say absorption-reemission, that is not true for most cases of refraction and reflection.
Your question whether the angle will be so that the wavefront will or will not enter the new medium is based on the molecular structure of the new medium. And in some cases, both happen at the same time. Some part of the wavefront will be reflected and some will be refracted.
But at the QM level, it is always the interaction between the photons and the atoms of the new medium that decide, so the molecular structure of the new medium.
