Query for more indeepth explanations....

[BlueTemplar]

Also, how well you can use the space available depends on your racial bonuses. And when you research orbital mining, you become a lot less limited by how many planets you have - except for research and intel.
I even wonder if it's not too powerful : orbital mining in combination with base space yards gives you practically unlimited industrial growth, while costing roughly the same than a new planet type colonisation tech.(for ALL 3 resources!)

It's true that the IRM system where population plays a lot more important role is more balanced, since in Se5 there is no "bureaucracy" to limit the effectiveness of the larger empires...