Ive been using a late 2013 rmbp 13" 8/2.4/256 and enjoying it. The only issue ive been having is the glitchy animations (mission control, swipes, launchpad) especially when using fullscreen apps and the adobe suite. When plugged into an external the glitchiness remains but when in clamshell + external its buttery smooth for the most part. The glitchiness is mainly aesthetic as it does what it needs to do just with a really annoying drop in framerate which gives the impression of sluggishness eventhough its still quick and silent. Im curious if the 15" with dGPU would be much smoother and possibly run cooler with the external connected NOT in clamshell. I would be very disappointed if i forked out the extra 1000$ for the dGPU and was still annoyed by glitchy animations and on top of it loud spinning fans. I primarily use a Windows desktop but I would like my laptop setup to be comfortable for xcode + photoshop + external (ATD) NOT clamshelled. I originally chose the 13" to be more portable when I go meet clients but I'd rather buttery smooth performance if its possible with the 15". Would the dGPU show large improvements for my needs? Edit: I dont play games and dont plan on using the laptop for video editing.