I've been musing on this issue (God, not God, what kind of God, where God, why God, etc.) since childhood, like everyone else, and even now haven't come to any firm conclusion. In DOF I've got a fairly extensive discussion on my current views on God and religion, views that are essentially work in progress.
In a future book, after I've finished doing the governance reform stuff which is most important to me, I'll discuss some of these things in more detail.
But I believe that the issue is not merely an empirical or logical one, it is also a practical one amenable to cost-benefit analysis just like any other economic or social policy issue. That I am proposing such a test doesn't mean this should inform state policy. Just a matter between us as private citizens. [Btw, I'm sure many others must have thought likewise about such cost-benefit analysis in the past – I simply haven't had the time to research this thought further at this moment.]
Benefits of God
A modest level of (tolerant) belief in God seems to provide at least some benefits:
a) Couples become more faithful.
b) Those with depression recover faster.
c) Those with alcohol addition recover quicker.
d) Cancer patients live longer with prayer and possibly die happier.
Costs of God
Excessive (fanatical) belief in God imposes severe costs on society. Such belief makes us want to kill those who differ from our conception of society and God.
We have seen examples in Hitler the Protestant Christian who killed millions of Jews. We have seen how Catholic Christians killed Protestants on St. Bartholomew's Day and at Beziers. We have seen how fanatic Osama Bin Laden killed Western Christians (at least that was his goal). And we have seen how Baba Ramdev would (if he could) kill 80% of the world's population because it eats beef. And so on.
The costs of God (or, rather, organised religion) become high when people become intolerant of other's beliefs and modes of living. Then religion's costs can significantly exceed its benefits. God (or, rather, organised religion) can potentially impose severe negative externalities. We just want an optimal amount of God, neither too little nor too much.
There is an optimal level of belief in God when maximum net benefits are obtained. That point is reached very quickly (starting from the border of agnosticism) and requires some level of fuzziness and modest level of belief (or not too much disbelief), just a tinge beyond agnosticism.
After that point, we tend to want to impose our views on others, forgetting that God (if He exists) is competent enough to take care of Himself and doesn't need our help to kill people. He can do so Himself!
Thus, Baba Ramdev forgets that he need not worry about trying to kill 80% of the world's population as their punishment for eating beef. God can pretty much kill all those people Himself (if He desires). That He does not seem to be interested in killing people for beef-eating probably means He doesn't really care about this petty issue (of course that doesn't mean we use such a fuzzy test while evaluating the fate of murderers!).
In any event, it would appear empirically that a modest level of belief is perhaps prophylactic and curative (within reason). Atheism does not seem to offer either logical or other benefits. No one can prove that God doesn't exist, so it seems to be an intellectual, emotional and spiritual dead-end. A wasteland. Agnosticism and a modest level of belief both deliver at least some benefits, with optimal benefits achieved with modestbelief.
Then, at the other extreme are those with fervent and fanatic belief in particular forms or shapes of God. Such excessive belief (being blind confidence in our imagination) is likely to be unwarranted, and its overall impacts on humanity are likely to be negative.
So the recommendation is: Don't go overboard in your confidence that you and God have a special relationship that authorises you to kill other people. Let God do His own killings Himself. There is no need to become God's helper in such things. Be His helper in doing good. I'm sure He'll be more pleased.
ADDENDUM (Notes for possible further work on this topic)