It's not the size of the boat; it's the motion in the ocean
Seriously though, I prefer 15" just because 17 is neat but kinda too big for the whole laptop thing and the 13 just feels too small. Of course ask a question like that and 10 people will probably give 10 different answers
Interesting that the 17" remains very much niche. I have not exactly caved in to the 15" rMBP as yet, but I have been hands on with it, and I've also put out a feeler as to the value of my current MBP 17"
The retina display may compensate for the loss in real-estate, but I'm still sort of on the fence....So I voted 17"
17" is the Mother of all notebooks because the MacBook Pro is for PROSumers standard, ultimate size, you don't pick this up if you're just wanting to look good at a cafe, you'll look stupid or dramatic for sure. Show off !! Plus cafes are for socializing or relaxation, for those who have notebooks at cafes - man - lame-O ! Grow some muscles and quit whining about "lugging and weight", get over it.
I've tried everything from 11 to 17 inches. If I'm going to own only one notebook then the 13 inch is my favorite size.
I found 11 inch screen to be a little too small for getting work done and using for long hours. The 15 and 17 inch have a bigger footprint than I like for using 'everywhere', such as on my lap or in cramped quarters when traveling etc.
Right now I have the 13 inch retina MacBook Pro with 768 SSD and it's the best laptop I've ever owned. I like it more than my 13 inch MacBook air because of the screen, it's quicker, has more ports and even a smaller footprint.
I have a Mac Pro and other computers and tablets but my new 13 inch retina is my go to machine. I use it more than anything else, my Mac Pro sits at my desk and collects dust but it works well as a server and for occassional heavy lifting tasks.
I have a 15" MBPr that replaced my 2010 Air. They weight is OK for traveling, but the size was uncomfortable in trains etc. Therefore I also got the 13" rMBP which is perfect! Now I use the 15" mainly at home only. Before the Air I had the 13" cMBP which has the same weight as the 15" Retina and I had no problem with the weight. The main reason I changed to the Air was not the weight but the higher screen resolution.
It's definitely the sweet spot between the 13 and 17.
Apple doesn't make 17" laptops anymore, so the choices are 1115.
I think if you do a lot of work and need a 17", the 15" is super nice and you just need to get an external display and plug it in when you get home. A 17" is a bit too heavy to lug around and most of my friends who are designers definitely complain after they get the 17".
I went with the 15" in the poll and in real life.
I tried an 11" MBA at the apple store and found the screen and text too small. The 13" is great mobility wise but the lack of screen real estate was an issue for me (running lightroom, photoshop and gotomypc).
The 17" is just a giant monster and its portability is less then that of its other smaller brothers.
That basically leaves the 15" which to me is the sweet spot in laptops and I own a 15" rMBP