Let's say, for example, that GIMP has an extra awesome macro-recording/playback capability that makes Photoshop look like a toy in comparison. (I don't know if this is the case or not so please forgive my ignorance.)
I forgive your ignorance, but I feel compelled to respond here by saying that it's actually the other way around. Photoshop has an awesome recording/playback capability (called Actions). You just hit record, perform the steps you desire, hit stop and there you go.
With the GIMP the nearest equivalent are scripts, but you have to write them yourself using a pseudo-scripting language. There's no simple recording feature, and I wasn't going to sit and waste time learn how to code up a script for an equivalent workflow of what I was used to doing in Photoshop, because the scripting is actually very complicated, particularly if you can't find the commands to do what you want.
People have complained about this (from 2001! - https://bugzilla.gnome.org/show_bug.cgi?id=51937), but nothing has happened because as the last post in said thread says, "we simply don't have
enough developers."
I won't bug them about it, but I won't bother with GIMP anymore because it simply lacks easy of use and important functionality. Open source doesn't always work in practice.