I stress the meaning already given to the words 文 and 武. According to them and trying to explore the hidden sense of the two statements, I think the sentence only makes sense on its first formulation(文无第一武无第二), the second one looks like a slightly rhetoric and pro-war interpretation.
In fact as 文 is a matter of self-personal and gradual improvement that you only are able to porsue if you are prepared to accept that there is no definite or best way (无第一). All attempts and little steps are useful to progress into. So, it's a painful process of continuous improvement, plain of multiple attempts and fails (a trial an error method) which, despite all the difficulties you find, you must be ready to proceed in its search, without never knowing when and if you are reaching the end (无第一).
On the contrary, fighting 武 is a more objectif thing in which you must make use of means at yours disposal to achieve, in that real moment, the goal and the aspired target- victory; giving your best in a life-and-death struggle, because there will be not a second chance (武无第二).
If you try to imagine a noun after the numeral of that sentence, like“way”or "opportunity” perhaps you can clarify its meaning:文无第一(道路/机会)武无第二(道路/机会).Huli