All of you sit down and play a decently-long game as all three races before you go and try to give suggestions. The game plays very differently from the viewpoints of the different races, so make sure you know what you're talking about before you start talking.
TEC starbases can build ships and self-destruct, but are immobile and have no weapons range to speak of. Their mines cost resources, are built from the tactical slot menu, and can only be built in controlled gravity wells.
Advent starbases can increase loyalty, promote culture, and automatically have two extra fighter squadrons, but lack front-line utility vs TEC and Ventari starbases and are immobile. Their mines are manually deployed from hangars and carriers, costing nothing and replenishing quickly, even in enemy-controlled gravity wells.
Ventari starbases have increased health and the ability to shrug off a certain amount of damage, as well as the unique ability to move around a gravity well to persue enemies. However, because of their slow speed, they are prone to chase scouts around if you're not paying constant attention to them, and are playing solitaire with themselves at the far end of the gravity well when the enemy attack arrives. Their mines are deployed by specific minelayer ships that are very difficult to control and direct, making them more useful to "tag along with" a regular fleet and drop their mines directly on top of the enemy forces. They are also free and can be placed in an enemy-controlled gravity well.
Now that you have learned a little something about the different race's starbases and mine-laying techniques, GO OUT THERE AND PLAY AS THEM AND LEARN EVEN MORE FOR YOURSELVES!!!
Have a nice day.
/smile