Wikia – “If Tali does not survive the events of Mass Effect 2, her role in Mass Effect 3 is replaced by Admiral Shala’Raan vas Tonbay.” Actually it’s Admiral Xen but w/e. With destroy you essentially commit Geth genocide and kill EDI, and synthesis, while saving everyone is neutral because of the forced change to everybody. Geth, EDI, organics all remain exactly the same.
One that can be determined by starting ME3 with a default Shepard as it’ll decide on the choices done in ME(1) and ME2. While there is no decided canon ending, as KnightEnchanter states, there is a canon playthrough of Mass Effect. Synthesis is by far the most moral of the options as you not only save the lives of that 99.99999%, but you also end their suffering in a much more positive way by actually ending their suffering, rather than their lives. I found the ending of the trilogy to be some what soul crushing. The poor reaction was because the series just gave you a choice of three outcomes (which were essentially the same in terms of the denouement afterwards), rather than the end being shaped by the decisions you made beforehand.
