I think the real question is how you plan on using the computer. My daughter picked up a 13" MBP last year, but she went for a top spec i7 3.5GHZ with a 500gig SSD drive and 16 gigs or ram. The key point is that most of the time it’s plugged into a 27" 4K display, but if she needs to take it somewhere it’s really portable and the size is fine for web browsing or email.
For actual development work, I wouldn’t really want to work on any display under 23" and when Norm’s new preview app comes along I may even bring in a second display for working in Blocs. At the moment I’m still working with an 8 Core Mac Pro tower, that is aged but still significantly faster than the MBP in Photoshop etc.
I’ve run Blocs quite happily on a 2007 iMac, so Blocs is very accommodating in terms of not needing terrific horse power to get things done. Compare that to Rapidweaver, which is the only app on my computer capable of provoking spinning ball on a regular basis.
On a different note, I’d be interested to hear from others how you find Apple laptops for general usage and especially for processor intensive work? When my daughter’s MBP arrived I ran a couple tests in Handbrake etc and the speed was generally good, but the fans kicked in immediately, which made me wonder if they are really built for intensive work.