I have been using the ANSI keyboard layout for many years now and stronly prefer it over the ISO layout. The ANSI layout has the smaller enter button and a longer left shift key. Then I use the US international layout such that I can create German umlaut characters and other fancy things. On top of that I use the Linux compose key to create even more characters.
The issue the sheer variety of US international keyboard layouts. Every time I set up a new computer, I end up having to cycle through all of them to find the one that I actually want. There are two major differences: One is whether there are more accented characters or more symbols. The other is the presence of dead keys. I absolutely hate dead keys, I need those accents on their own for programming. Curiously the one that has no dead keys has “dead keys” in the name.
But there are many other variants, which don't work for me.
There is the variant which just has the EUR currency symbol on the 5 button, and that's it.
There is one which has dead keys in it, I really hate to use those. Apparently the difference to my favorite one is that the dead keys are without AltGr, whatever that means.
Then there is one which only has a limited set, that perhaps was a basic variant at some point.
If one wants to compose characters with lots of accents, this variant might be very nice. There they act as dead keys and one can hit multiple dead keys in order to form a letter with arbitrary many unicode decorators attched to it.
And there is a different variant, but I am not sure what is different.
These are great keyboard layouts, one just needs to know which one is for programming and which for international languages.