Late 2014 vs 2015 IMAC 27 Retina

RCGJR ~ See the table "Specifications of Slim Unibody iMacs from 2012—" HERE.

The link you were provided does not answer the question(s) you asked. To get the correct answer navigate to:

http://store.apple.com/us/buy-mac/imac-retina and then look towards the bottom of the web page where a comparison of the models is discussed. You will see the primary differences are a spinning 7200RPM standard HD vs. a Fusion drive and the difference in the GPU.