Material preview is rendered by Blender Internal while the actual render is generated by YafaRay.
They are very different render engines and the material settings do not have the same effects in both. You might have to further tweak the YafaRay material reflection settings to achieve the shine you want.
For a more YafaRay-realistic material preview, go to the Material or Texture tab, show material preview small window, and enable the Preview Controls. It will allow you to move around the selected object with the desired material, and it's rendered by YafaRay.
For a video showing how to do it (it's for an older version but the procedure is the same) see:https://www.youtube.com/watch?v=jEHuVyjF1OI
(the video has no audio, sorry about that)
I hope it helps.