IIRC, the multicore performance of the new 2017 MBP dual cores now are roughly comparable to your 2011 MBP in terms of benchmarks, where as the MBP dual core CPUs of the last half decade+ have not. With certain tasks, the performance difference between my 13 and 15 is most dramatic. Where as my 13 is a great mobile machine, my 15 is my workstation, and my 13 could not do a good job filling the roles of my 15 if it needed to be my primary machine.
If your work is CPU-heavy and this is your main system, I would personally lean towards the 15-inch because, 1) you are already accustomed to the performance of the quad core CPU maintaining technical relevancy for an extended period, 2) if you do not often use an external display, you may find the extra screen real estate is an asset for certain developmental work, 3) I feel it is likely that future versions of OS X will place more emphasis on GPU offloading (so if it were me I would also get the 560 dGPU upgrade), 4) You kept your last machine for 6 years so getting more performance now could potentially equate to a longer service life. This is all my personal opinion, of course.