Um yeah um
This isn't Starcraft really.
It really comes down to what map type, what you plan on doing, what your enemy is doing.
Colonizer Capital ships are a good use of your free capital ship but I and some others prefer a more aggressive approach and go for a Carrier Capital ship plus a Colonizer Frigate. Sometimes a small forces you to go aggressive whereas a big map or easy AI you can go Colonizer Capital ship. After that its a bit in the air.