Point is if all pull their own weight regardless of unique features they will all do better. If only one is pulling the weight for all of them, it's pretty much a lost cause.
Now that's looking at the bigger picture
There is a twist to it: If I recall right, the income is divided something like this:
The profit from a player goes to 35% to the planet he originated on, and to 15% to the planet he's doing activities on (and 50% to MA).
So a planet partner who does lots of advertising and brings in lots of new players will earn more than a planet partner who is good at pulling people born at other planets to their planet. In other words, external advertising/promotion pays better than internal. And of course it's optimal if a planet partner both recruits his new players (from outside) and then stay and do activities on the planet.