Hi there, I recently sized this consideration up and with with the 12" MB. Like you, I have a top of the line 15" rMBP through work and a 27" (older) iMac at home.

While you didn't say it I'm assuming you want the 12" for an on-the-go, everyday carry to take between home and work. At least that was what I was seeking. I do a bit of design and development but really got it for research and writing papers (yaaaa grad school).

All in all, it's a fine little machine but I would probably recommend you go with the 13" rMBP. Here's why:

• Despite being called a laptop, a 12" retina screen becomes hard to read when sitting in your lap. Real estate aside, it's hard on the eyes at that distance. For instance, I typically have to bump google docs up to 125% or zoom in on pages. I didn't think this would be a problem as I used to have one of the old 12" macbooks (that was a decade ago, man I'm getting old) but it totally is.
• It's bouncy in your lap. No seriously, it's so light that typing in your lap is wobbly.
• It really struggles. I got the baseline model and things like google docs and PDFs in Chrome cause it to lag. You'll notice things like the interface stuttering when switching between full screen apps. I haven't done a lot of design or coding on mine (yaaaa grad school) but judging from my experience thus far, you will be frustrated.

Now for the pros:

• It's light, like super light. This makes for a great everyday carry.
• It's small, if you have some big backpack (30+ liters) you could totally downsize to something around 20L and get by.
• It's really sharp looking
• I actually prefer the keyboard, it feels nice and oh yeah, force touch is a gimmick.
• Ok, really, the pros are that it's small and light.

Hope that helps you.

Edit: just noticed you went to NEU, huskies represent! Also, I work right off of Alewife so Cambridge/Somerville represent too!

I bought both, the mb 12" 1.3Ghz and mbp 13" 2015 base model, and worked with them for 2 months. I do photoshop, sketch, sublime text, ( front end developer ) and by far I recommend the mbp.

The mb lags a lot while the mbp does the job much faster and no lag at all. I sold the mb and kept the mbp.

Hope that helps.

Bang for buck 13" rMBP. If you can live without retina then MacBook Air; save yourself some money and still have better performance.

12" is dramatically more portable, 13" is dramatically more capable. simple matter of what you need.

I'm pretty much in the same boat, and have a similar set up and pattern of work.

When the 12" MB came out, I was a big hater. Then I saw it and changed my mind. lol

I went with the 12" MB and love it.

It's not my primary workstation, but the big thing - I take it everywhere. Battery life is great and it travels well.

Runs Sketch and other programs fine, as others have said.

And, I'll leave the 12 MB open and go back and forth during the day just to take a break from the big screens.

My setup:

I was recently in your same position. I decided to go with 13" rMBP. I actually like it better than the 15" rMBP I use for work. When you compare specs side by side with the 12" mb, it just feels like you're getting taken for a ride with the MacBook. It's a beautiful piece of hardware, but unless they drop the price the 13" is definitely the better option.

I have a 15 retina MBP and wish Apple would release a 15 or 14 inch Macbook Pro that is lighter and tapers like the MBA and comes in Space Grey. I would buy in a heart beat. In your case I would go with 13 as the extra real-estate and performance will be better suited to UI/UX work on the go.

I got the 13" MBPr and upgraded to 3.1GHz and 16GB RAM. I run a development environment, Sketch, multiple browsers, Spotify, Slack while plugged into a 27" cinema display as well and it kicks ass.

I also manage to get 60FPS in League of Legends for those that have spare time to game on weekends :)

Love the machine. Won't go back to 15"

I have both the 13 rMBP, the 12 MB.

I do most of my on my iMac, while occasionally take my laptop outside for meetings and casual work/writing sessions in coffee shops around. The 12 MB does lag from time to time when handling medium to large Sketch files. Think 10 - 20 iPhone 6 screen size Artboards on a page, while the 13 rMBP handles most situations very well. However, I honestly think this is due to some poor file handling optimization from Sketch, rather than the lack of CPU power from the 12 MB. (Hope this could be improved overtime.)

I tend to not to do any serious work on laptops because the smaller screen sizes really limit my productivity. In my opinion, workstation is for work, laptop for portability.

Bottom line: Try to picture the scenarios when you'll use your laptop. If you see yourself spend hours working on it, then go with 13 rMBP. If you simply use your laptop as a companion sometimes, just to have a mac with you on-the-go like I do, then 12 MB will serve you just as well, with a smaller footprint and less impact on your spine/shoulder.

I haven't used the MB 12" very extensively (just in the Apple store for a while) but I'd shy away from it for several reasons. I do own a 2013 rMBP and I've owned a 13" MB Air as well.

Connectivity - Sooner or later you're going to want to plug something into it. This might be the TV in your client's conference room. It might be a HDD, your phone & the charger. One USB-C port is going to make that at the very least difficult and you're signing up for adaptor hell. Sure it's "only" $80 for an adapter but those will add up quick...

Keyboard - I can't stand the keyboard on the MB for a decent amount of typing. Some people love it, others don't so your mileage may vary BUT if you need to write code and you hate/aren't accurate with the keyboard your only real option is an external KB (see above).

Screen - 12 inches is quite small, especially with the higher resolution. I think you're just asking for eye strain when you're writing code or dealing with the Sketch interface. That diagonal inch on the rMBP makes a bigger difference than you might think. You could always plug in an external monitor... Oh wait Apple doesn't offer a USB-C monitor yet so even with an adapter you'd lose the benefits of the extra connectivity...

Honestly I think the price on the MB 12" is way too high for what you actually get (specs wise). It's not significantly more portable than an Air and the Air has more connectivity options. Plus you get quite a bit of computer for the price in the Air.

If you want portability above all else I'd look at an Air. If you're going to use it very much (which sort of seems like the point) then I'd suggest going with the rMBP.

13' RMBP doesn't lower it's clock speed when it actually gets under a heavy load so it's a no brainer for professional work

I have that 13' rMBP and looove it. Zippy and portable. Never had an issue in Sketch.