I might be accused of being a re-hash but here are some more peanuts to toss into the gallery and it applies to not just people doing photography.
1) Get an idea of what applications you will be using and research best hardware set ups.
As example, some apps only require 1 core vs multi-core, some take more advantage of the GPU and of course RAM.
2) Decide what best meets your physical needs as in small vs larger laptop.
3) Realize that with many Apple products, ability to update later the hardware internally is a big NO so you will need to ideally plan ahead.
4) Some hard core users realize that as time moves forward, the need for a bit more power or drive space should be anticipated at purchase. The key items - CPU, GPU, drive and RAM. (again check the apps you may wish to use)
As someone who deals with image files and Photoshop, I was more concerned about RAM and minimum drive space. The GPU wasn't much of a factor and so I did what I felt was the sweet spot for price and hardware - Middle line processor mid 2015 2.5 i7, 512 SSD, 16 gigs RAM (MB pro). I also run Capture One, and a few other photo/graphic related apps. This works well for me, you might find that your needs are quite different but the point is, I did my homework and it paid off.