Accepting that agnosticism is the default position of science with respect to the possibility of most things (including god), shouldn't atheism nevertheless be considered the likelier conclusion when compared to deism?
Note: I'm defining deism I think in line with conventions, which say that deists believe the universe had a godlike creator who initiated the universe but has since taken a more hands-off approach. Theists are welcome to argue their case for a personal god, whilst (I hope) acknowledging this is the less defensible position.
I don't want to start any quibbling about the strict definitions of terms here, but I take it you mean that atheism refers to the act of denying the possible existence of a god or of a creator of the universe. I believe, from a philosophical or even a scientific point of view that is a pretty tall order. The current state of science (the standard model) is the theory that the universe started with a big bang, in mathematical terms, a singularity or something entirely undefined, about which nothing can ba said or known at all. That is a rather far distance short of excluding any possibility at all. Indeed it is no explanation at all - i.e. "the universe started with a huge concentration of energy about which we can say nothing at all" doesn't appear to me to be a final statement with regard to that or anything else for that matter.
That the natural world appears to operate in accord with a fairly small set of "laws" that are at least partly discoverable and knowable by men (i.e. evolution) says nothing whatever about its beginning or existence.
It is a rather simple matter to debunk or show the inconsistiencies in any religious dogma of any form or to note the lapses and contradictions in the behaviors of nearly any group of believers. However, that doesn't resolve questions that have perplexed humans of all known cultures over the centuries of histories about which we have some knowledge.
Based on all this, and the strange enthusiasm (and ironically amusing credulity) with which some atheists embrace these "explanations" as final, I'm inclined to put my bet on a creator of some sort. However, as Lustig pointed out earlier in this thread, neither belief can be proven conclusiverly to its opponents.