Wow, I’m really impressed as to how a lot of people think. I liked all the endings for the extended cut, they all were good. On a personal opinion, I actually don’t know which ending to chose. I tried to weigh the pros and cons of each. My personal choice was destroy because it’s basically what I set out to do from the beginning of the trilogy. I didn’t give it much thought at the time, but my first play through I chose synthesis because it “seemed” like a happy ending and I was also confused as all hell, that catalyst…. Anyway I thought synthesis was (WAS) a good idea because it takes a new step in evolution and I think at some point in time everything has a final stage of evolution (Or least a prolonged state which evolution ceases). Like in 2001 A Space Odyssey (*Spoiler if you’ve never seen that movie*)
(The god child)
(I’m talking from the biological standpoint) Evolution happens so something can adapt to a new situation (Over time of course). In synthesis your forcing the galaxy to “evolve” to maintain galactic peace. (Which is a nice thought). Whether you agree to this or not is your choice (you really weigh the scales on this one). Since you forcing this evolution it’s a “man made change”. Thus defiling nature. I don’t think it’s a terrible ending, but I feel no matter what some kind of inequality will arise and this synthesized peace will not last forever. I feel synthesis is too good to be true. You get what you want (Peace), but in the end what it really is, is not what it seemed. And the Reapers like the Geth have the will to survive and they’ll do it by any means necessary.
So to put this bluntly, I destroyed the cuttlefish looking robots, avenged the millennium worth of lives they killed, and ended this viscous cycle of galactic genocide!!! But that’s the point of the endings you chose what you wanna chose

!!! And I felt all three or should I say four endings on the extended cut were all very well done.