TEC focusses on credits, Vasari on recources
Advent are somewhere between, however, u can get around 90% of TEC credit income and 90% of vasari recource income, if u play smart
first of all, Progenitor coloinze ability reduces infrastructure upgrade, this is the best colonize ability in the game
secondly: advent have a tier 3 tradeport, means they can get credits pretty easily iit's also combined with a refinery.. if u bother upgrading it meaning u can save alot of logic slots by putting amassed trade ports then switching them back and forth between cash and refinery (neeaat)
advent have easy-to-get culture buildings.. alot of peopel often ignore culture and use/think it as a form to take over planets,
in fact culture does alot of things, 1. increases planet's allegiance, higher allegiance means more loyalty, means harder to overthrow , means more income $$$$ (prolly cheapest way of extra income, since u only need 1 center every 2 planets to get good spread (1 per planet if enemy is deploying its own culture tough)
2 increases antimatter regeneration i bet u didnt know that one huh
? and guess what, advent love antimatter what nifty duo 
3 if u invest on culture enough you can put some serious strain on your enemy, him having to deploy culture centers of his own or sending capital ships to prevent a loss of a planet
so, to be honest, i've never made more combined income with TEC or vasari then with advent, guess the unity truly is unstoppable....