That would depend where you live. I wouldn't want to do either in Saudi....

I've never had to come out as LGBT but am frequently reminded how hard it is to come out as an atheist. Living the the US which was built on the premise of religious freedom you would think that it wouldn't even be an issue. But openly stating that you don't believe in god seems to be an invitation for people to try to change your mind. It feels as if being a good person is thought to synomynous with being devout.

I don't think it's reasonable to compare the two.
Both can be extraordinarily difficult, depending on the circumstances.
It's going to be different for everyone.

I imagine LGBT would be more difficult.

For me, mentally it was being childfree (aka - I really hate proto-humans). I got a tubal at 26 - and neither parent showed any surprise. Apparently my memory of threatening to drop a toddler when I was only 5-ish was a major clue (it was sticky), and early teens asking about a hysterectomy, had prepared them. My dad was an unrepentant ATHEIST, so that was a no brainer; and I have always been more a-sexual, with a definite preference for being cis when interested.

I have just joined and this is my very first post. That being said, I don't know which is harder. I am an Atheist and when the question of 'do you believe in god' has arisen, I've honestly answered, "No, I'm an Atheist". Suddenly, everything changes at that point. People react to me differently as if I had some horrible communicable disease. All I've done was answer a question; I'm not trying to convert anyone. There's no insidious agenda, just a statement of fact about myself. I imagine the experience is the same for the LGBT. We are all human and different in one respect or another, and since we are all different, we are all the same. I'm hurt by those who shun me for what I am, but I move on. That's the best answer I can give.

I had multiple coming-outs (Asexual, then Gay, then Transgender, then Intersex, currently Intergender/GNC) and now as an Atheist, too.
The worst & most painful was coming out as Asexual in High School & Community College, it really bit.
I got the kind of rejection from friends that's normally associated with coming out as LGBT, and it was from "Gay-Friendly" friends in the Theatre Department, no less. AAAGH!

LGBT. No question.

I don't see how coming out as an Atheist is hard. Perhaps, I've just always been a bit bull-headed with my idealism... that, and my family isn't particularly religious to begin with. I have a few religious friends but we just don't discuss theology and we're good.

It really depends on those around you - If you have a liberal, accepting family & friends (as my friend did), coming out can be a great experience. If you're a Mormon
on a commune, coming out (and escaping) would be a whole different experience..

Based on opinion surveys, in the US atheists are less accepted, but I'd be curious to hear actual experiences from people who have come out as both.

It would probably depend who you’re coming out to, your parents, your boss or your friends. It would also depend on your age and where you live. I live in one of the most conservative areas of Arizona and have had no problem as an atheist but I imagine that a LGBT person would have a greater kickback around here.