I hope this doesn't result in Mac vs PC bashing, that is not my intention. But, here goes...
I have a MBP mid-2012 Retina, 2.6 GHz Quad Core I7 Broadwell/Haswell(?), 8GB RAM, 512 GB SSD, NVIDIA GT 650M 1024 MB, Intel HD Graphics 4000 1536 MB. I am now working with much larger raw files than when I acquired this MBP, multiple layers, filters, etc. Phase One recommends: CPU with 4+ cores, 16+ GB of RAM, Solid State Disk (SSD), a fast Graphics card from NVIDIA or AMD with 2GB+ RAM (4+ GB for 4k or multiple monitors).
I intend to run laptop with 4K or 5K monitor, editing of still images only, no video. Also, no gaming. I have looked at 2016 MBP with Touch Bar, and I do not think the price/performance makes sense for me, at this time. So, that leaves me with a couple of alternatives:
1. max'd out 2015 MBP Retina w/2.8 GHz Quad Core I7 (Haswell/Crystalwell?), 16 GB RAM, 1 TB flash storage, AMD Radeon R9 M370X 2GB and Intel Iris Pro 5200, or
2. transition to PC such as Dell XPS 15, Quad Core I7, 2.6 GHz Sky Lake or Kaby Lake, 16 GB RAM, 1 TB PCiE , NVIDIAŽ GeForceŽ GTX 1050 with 4GB GDDR5, etc
The 2015 max'd MBP is approx 15-20% more $$$ than Dell. Staying in Mac OS offsets that difference, but not at the expense of real world performance. I am not a techie on computer specs, so my question is "Are these two laptops comparable in terms of performance for photo editing?" I realize the Dell is newer, but in reality is there a significant difference in the performance I should expect. By "significant", I mean 20% or 25%+.
Again, I do not see this as a Mac vs PC issue. I see it as a price/performance/convenience.