Greetings - I just wanted to give a comparative analysis of the speed difference in the two new rMBP models under 'normal' everyday use. I looked at all the Benchmark stuff and disk write, blah blah blah but they never say what you can expect. So I just bought a 15" for work and a new 13" personally. I put a movie together, copied to both and rendered. Here's my results - Both machines - Late 2013 rMBP 8GB Ram, 256GB, iMovie 10.0.2 15" is the i7 2.0 Quad Core. (Stock $1999 machine) 13" is the i5 2.4 Dual Core. (Stock $1499 machine) (Both were also plugged in during transcoding) Movie CONTENT source is about 32GB of 1080p, and a few dozen pictures in iPhoto, along with a ton of transitions. Final movie is 35 minutes, 3.19 GB final size in 720p and 5.28GB final size in 1080p. Here's the time to transcode to an MP4 file for the two machines and two resolutions - 15" 1080p 15 minutes 13" 1080p 20 minutes 15" 720p 19 minutes 13" 720p 27 minutes What I found interesting, is that when USING the 13" and putting the movie together, I didn't find it much slower than the 15". Both moved clips around, and copied, with VERY few beachballs. I guess I was expected the 15" (Quad core) to be much faster and it was at transcoding. 30-40% But in everyday use, both are lighting quick at startup, restart from sleep, numbers, etc. And that's compared to the machine i replaced - 2010 13" MBA. Both machines in transcoding did have the fan come on about half way through the 720p movie, the 15" sounded louder, but both relatively quiet. And both never got above slightly warm to the touch. So I guess, if I could only buy one, I wouldn't hesitate to get the 13". It transports easily, and I find the 15" a beast to carry around. But again, I'm used to the old 13" MBA. The screen on the 15" does seem WAY bigger though. Just that extra 2" I think makes a huge difference. So for the extra $500, the 15" is probably a better deal for power users. But for everyday use and transporting, there is NOTHING wrong with the 13". I love it. That will be my primary machine, period. I'd only use the 15" if I had big projects to crunch. Hope this helps. D.