I find that income is more important than just population (though pop will create a nice income as well, so higher pop planets also tend to have better income). If the planet has a high class yet still a low population, and has a nice income already, it will potentially grow pop and have an even better income. Though, in practice, I do generally go for the home planet, as they already have a decent pop cap, and often gets the Central Bank. Distance is always a good thing.
