The general consensus in the current version is (overall) Vasari > TEC > Advent
On more expansive maps, I'd say it's Vasari > Advent = TEC
On tiny maps, I'd say it's Vasari = TEC >>> Advent
TEC has the best economy and great value military units. They also have excellent repair capabilities. Unfortunately, they lack any fleet support capabilities and tend to get overwhelmed by the other faction's late game technologies. Their capital ships are very weak at lower levels, meaning that unlike the other factions they're almost a complete waste of money until they gain a few levels, which makes it much more difficult to recover from losing one.
All this makes the TEC a faction which can completely roll an opponent by carrying over a strong early-game advantage, but if you make a slip-up their late-game prospects are downright terrible.
The Advent have an absolutely atrocious early game, and in general are considered hopeless in a rush scenario, particularly in the vs Vasari matchup. If you can survive to the mid-game and bring out their more powerful abilities the Advent can become quite formidable, but getting there is the challenge. They have excellent capital ships, awe-inspiring fleet support abilities, and excellent firepower. In the mid-late game, Advent is definitely at their strongest and can easily go toe-to-toe with fully upgraded starbases and barely take a scratch.
Overall, Advent comes across as a late-bloomer faction. Surviving the early-game is the difficult part, and this is why they're generally considered the weakest faction. If you can get past that, they're actually quite scary in the hands of an expert. Their economy is a little weak, but they can still trade spam and their tendency to accrue few casualties in battle saves them money.
Finally, we have the Vasari, undisputed kings of the current version. They've basically been the underdog faction since the early days of Sins, but have pages upon pages of special advantages they can deploy against the other factions. When the right combination of buffs and nerfs hit last patch, they went from underdog to champion very suddenly. In my opinion, a top-level Vasari player on a balanced map is effectively unbeatable. They'll surpass the TEC's economy by capturing the neutral extractors, their best combat units are available from the word "go", and they have absolutely scary late-game abilities to work up to.
The Vasari economy is a little slow to start if you don't have neutral extractors to access, and their units are otherwise quite expensive, but these are pretty much the only Vasari disadvantages and they compensate for these in so many ways it's just not funny. As TEC, you need to hit early when your own forces have better economic value to prevent the Vasari from reaching his more dangerous late-game forces. Advent needs to quickly get their higher-end units and special abilities to match the Vasari, but this is definitely the most slanted matchup in the game currently.
