Camaraderie is better than having a little more money.
Unity will help keep the cash flowing more than fighting for a few extra percentage points of a song.
When it’s lopsided and the singer or the primary songwriter shows up in a Porsche and the other guys are still driving Pontiacs, it’s going to fall apart. Porsche guy didn’t do anything wrong, the band just isn’t going to last.
As legend has it…
For U2, it’s an even split across the board. All four guys get the same.
For Coldplay, Chris gets 40% songwriting credit and the other guys each get 20% even if they didn’t write a single lyric or melody. And the band as a whole decided Chris should get a little bigger chunk because he’s usually the one writing the bulk of the tunes.
I’m sure there’s other ways to do it, but those two bands have stuck together for a long time so it couldn’t hurt to start somewhere around there.