Can asking "why" enough times show the difference?
Theist: I believe in god
Why? because the (bible/koran/etc) said so.
Why? because book in question has stood over centuries and consists of several written accounts.
Why? because written accounts = writings as people have observed events, and committed them to paper.
Why? because writing is based on a language, which itself is governed by a strict set of rules concerning grammar, meaning, etc.
Why? because human beings need to communicate with each other, as we are social creatures, and thus need a common basis for communication.
Why? because in comparison with our capabilities with creatures like tigers, we are not endowed with the requisite ability to survive alone.
And so on....
Now, the atheist:
I do not believe in god.
Why? because there is no evidence to prove such an entity's existence.
Why? because a phenomenon is supported by evidence, which is basically a set of observations and findings related to the phenomenon.
Why? because observations of a given phenomenon are intimately connected to that phenomenon by a series of steps, forming a chain.
Why? because each step by itself is a phenomenon, and can be broken down into further steps.
Why? because everything we do follows that rule. in essence, we are "wired" this way.
Now, you may observe, that if you continued breaking down the last "why" statement in the theist case, you will eventually arrive at the last "why" statement in the atheist case.
So instead of doing a top-down analysis, you need to start at the bottom. The difference immediately becomes apparent. Following the logical progression, you notice that the top two statements in the theist case do not have a rigorous foundation (in all fairness, none of the statements do, but they are *less* rigorous.)
Finally, I contend you have it backward. The theist "believes" in god and the theist "believes" in scientific rigor, but as you can see, it is not possible to believe in god without first "believing", or, using evidence in some form or the other. Thus the two "beliefs" are not equivalent, because on the theist side, it isn't as "rigorous".
Phew.