Actually, you ALWAYS get the colonizer on large maps when you need to rapidly expand.
Tactics become so diverse on small maps that there is no right answer. Different small maps even have different tactics. It all comes down to play style. One player might want to try to expand fast, and another will immediately start building a fleet built around a battleship or a siege capital. I will say this...if your enemy invests their money in colonizing 3 worlds and you spend most of yours on a fleet and immediately attack their homeworld, they are probably in trouble.
You're gonna have to figure out which ship you like the most for your playstyle. 
On Small maps, I tend to make:
TEC: Marza...sometimes a Kol
Advent: Progenitor....sometimes a Radiance
Vasari: Evacuator....sometimes a Kortul
