In the end, I chose to go with the firm that didn't pitch its shower or running culture. But, I was concerned about maintaining my running and had already started researching ways to pay for access to a shower so that I could run on my lunch (or, let's be honest, my dinner) break.
Yesterday, at lunch with some of my future colleagues from the firm, I asked about the gyms that people belonged to for the purpose of finding the nearest shower to the office. I was ecstatic to learn that the firm I chose has a shower in the basement. If only I had known, I could have broken the dead even tie and saved myself a couple of weeks of career decision anguish as well as gotten more schoolwork done (which I am now realizing is the main thing that's going to bite me in the ass from the first couple months of job stuff). Oh well. All's well that ends well. In hindsight, the career decision wasn't remotely as big of a deal as I had myself worked up to believe. I've made much bigger decisions in the past, most definitely will do so in the future, and no one really knows where or what they will be doing tomorrow, much less in a year.
Here's to not going completely bat-shit fucking loco. [raises glass]