I chose "destroy" at the end. The result was Joker, Tali, and Javik getting off the normandy. Tali makes sense to me since I romanced her in ME2 and this game. But Javik? I barely talked to the guy... I would have preferred Garrus :/
I went back and chose "synthetic", and the outcome was Joker, Edi, and Tali. So far, that is my favored outcome, and I am about to do "control" next, but I was just curious if anyone had figured out what determines the end characters.
Another thing they need to do is clarify what "synthetic life" means. I thought it would mean all forms of computer intelligence would die, right? That would hurt civilization the most I think... Thus, a good reason NOT to choose "destroy".
I chose "control" and the result: Joker, Edi, Tali. I can't answer why certain people are showing up at the end (perhaps bioware will tell us in the coming months. I am sure itching to understand. A cliffhanger like this is useless unless we can understand "what the cliff is")
My best answer for Joker madly flying through the Mass Relay, is that his assumption is that the "signal" not only could destroy him, but also kill EDI, for whom he cares very much. In the "synthesis" choice, you see that Joker has changed... So obviously the signal enveloped the ship as it fell apart.
In addition, what are your thoughts on the Relays being destroyed? For all intent and purposes, all life is now alone. There is no way to traverse the Galaxy so quickly. How can the game series continue if this is the case?