Honestly, I chose Synthesis Ending more often because it seemed like the right thing to do. Legion sacrificed itself for the Geth and EDI is Shepard’s friend, any ending that can spare both is the one I’m most likely to pick. The Control Ending also spares both, but it seems like it doesn’t honor the sacrifices characters made and doesn’t have as bright of future.
The ones I usually go for is destroy or control. Those are the only ones you Can build up on the Events of the current and final cycle. Synthesis feels like some fix all happily ever after ending and refuse which should be regarded as a bad ending since you fail to take down the reapers and the harvest continues.