I went from an early 2013 to an early 2014 rMBP 15 max RAM and Storage. The 2014 feels less warm probably because the fans spin faster in heavy use (6200 rpm). According to the iStat pro widget when heavy processing transcoding/rendering, the GPU seems to run as hot, typically 75-80C, the CPU not quite as warm, typically 55-60C at the heatsink... but I see wide variations in CPU temp. The 2014 seems to cool down faster. The 2014 seems to idle 45-50C, don't recall the 2013.
The 2014 has Crystalwell, however. Dunno if that makes a difference. It has discrete graphics, dunno how that translates to integrated.
The 2014 will feel more comfortable on the lap... but if you are gaming or rendering.... it may still be uncomfortable.