I will give migration props though. It makes population management so easy. Population increases really quickly on breathable planets without having to micromanage population transports and you don't lose any population from your homeworld being at the maximum population amount as many will migrate elsewhere.
When you capture races of different atmospheres - they'll start migrating to planets of their type, which you can then remove your own population and then make them undomed - reducing 50% of the work required to do this in SE:IV or if you prefer to just jettison your own people into space it's 100% reduction.
