The thing is, I'm only willing to kill the geth because it's the only option. If the destroy ending would have caused all of the quarians' suits to malfunction, killing them all, but sparing the geth, I would still choose destroy. The control is what the Illusive Man wanted, and Synthesis is what Saren wanted. Both crazy, deluded men. I don't really want their visions carried out, not with all the unknown consequences.

But I have to say, if any race was to get wiped out, it would be the geth. They just gained consciousness. They have no culture, music, art, government, history, etc. etc. yet. Killing them doesn't leave as big of a hole in the galaxy as killing, say, the asari would.