As much as I'd hope you read my post at the bottom of the first page, that aside, I have to take issue with your ME3 opinions.
Firstly, you're hinging the future safety of the entire galaxy on Shepard's disembodied consciousness against the collective AI of millions of years worth of Reaper-ised civilisations. Forever.
So Shepard is supposed to just lead the Reapers, milling around in darkspace for eternity, assuming their mind holds out. Even ghosts want to die at some point, I imagine Shepard would reach that point or go insane or become overpowered by the others. Ultimately, if Shepard still had some sense of moral duty, they'd probably crash the Reapers into a sun or Black Hole. There's still the possibility that Shepard won't hold out though, and then we have the whole Reaper issue all over again.
So, Synthesis. All life mixes together. Great, that doesn't affect the sanctity of life and free will one bit. And Shepard decides that future for everyone, in the whole galaxy, forever. Thanks, Obama. It's a terrible idea.
Or you can fight and die trying. Doesn't really resolve anything though.
Then consider Destroy. You sacrifice EDI and the Geth and save the entire rest of the universe. It's the least worst option by far. Yes, the Geth die, but everyone else survives. Looking at the options, it's not much of a choice to make.
And let's just go over those options one last time : Fight and die trying (Galaxy get harvested again), forced shared consciousness for the whole galaxy, Shepard becoming the dominant Reaper mind (which may very well fail over time, I don't think anyone can win against infinity. Reapers could very well return later) or sacrifice the Geth and EDI to put an end to it, there and then (Reapers die, galaxy can rebuild).
Destroy is the only real solution to the issue. All others allow the Reapers with the potential to return, only the details change. There is no inevitability that organic life will create superior AIs and cause the Reapers all over again, that's the Citadel AI's core programming speaking.
Like I've said before, I choose the path where life continues to have a choice in how their future unfolds. The Geth were victims of war, but I can't condemn everyone else for just one race, no matter who it was.