Not much actually, but for me it’s default settings of Goland vs “you need to setup some small things, plugins and shortcuts in Intellij IDEA Ultimate to work with Go effectively”. Ultimate is also a bit slower if you don’t disable a ton of Java plugins. But if you don’t need Java and disable it anyway, why not to use more streamlined and lightweight Goland?

the go plugin that existed at the time of goland creation and what exists today are very very different things.

the go plugin back then was very simple. The fact that you get most of the goland experience in idea ultmate today is because they are investing into the go ecosystem as an independent profit making endeavor in and of itself, not simply a small value add.