The reality is the OP can only afford one or the other and 16GB has worked just fine for years on all MBP's without issues. On a desktop machine throwing lots of extra RAM (more than 16GB) at Lightroom, FCPX and Capture One etc has little benefit to UI speed, render speed or processing speed. We are seeing more and more emphasis being place on GPU acceleration of the UI, render and general performance in Mac OS (Metal), Lightroom, Photoshop, Capture One, FCPX, DaVinci Resolve and many others.Why would you pay $2000 and more for a laptop with 16GB RAM in 2020 without the possilibty to upgrade it in the long run? Slower CPU, no issue, just wait a few seconds. 512GB SSD, no issue, work with external media. But not enough RAM? That really slows down your PC.
I don't get it why you would justify 16GB for this machine.