How to debate a Christian

[NoGodaloud ?]

Most atheists simply lack a belief of God. We have considered the claims of theists and whatever flimsy evidence they have and not accepted it.

then i guess you have a better explanation for our existence. what is it ?
if you answer : i don't know, i can help you out.

you have exactly more two options.

Wheter the universe has existed eternally, without a beginning, in some form, or it had a beginning with the Big bang, but without any cause. The Big Bang simply happended, out of absolutely nothing.

which one of the two do you prefere, and why ? and why do you prefere it over God as best explanation ?