Why I Made My Choice about the Geth in Mass Effect 2
I choose to destroy the Heretic's. Why? As a disclaimer I haven't played mass three yet.
Point One: The enemy wants to kill every sentient life in the galaxy and by all accounts they have pretty good odds of doing so. Anything is preferable to that; when the stakes are this high morality is a luxury we can not afford. Survival is the only thing that matters. As such I do not care in the slightest whether it is more moral to rewrite or kill.
Point Two: An ally you can't fully trust is of limited use. You can never be 100% certain the Heretic's won't go back to the Reapers; every time you'll deploy them you'll wonder which side they're really on. This severely limits their utility https://routerlogin.uno/.
I do realize this statement applies to Cerberus as well; while I do believe they'll sacrifice me or commit atrocities on aliens at this time I have no reason to think they will work with the Reapers. I could be proven wrong but I don't have any evidence to suggest that.
Point Three: The Geth don't object to me killing the heretic's and most if not all companions object to rewriting them. This suggests that it could endanger relations with other nations who could fight the Reapers.
Point Four: I've seen what the heretic's can do; and if they put a knife in my back that effect is multiplied many more than just with their military might. I'm not going to get another chance like this.