This is the crux of it, however it raises an issue that I haven't seen mentioned yet, the price of games.
It has long been argued (largely unconvincingly admittedly) that piracy "costs" developer money. If the MS DRM is shown to "work" then there is an argument to be made that the games released on both platforms should be cheaper on the Xbox (especially if the opportunity for earning more money on resale is there)? If the publishers buy into that theory and the Xbox One is cheaper to run then I think, for a lot of people, the question will become muddier. Similarly if publishers begin to see better rates of legitimate purchases on Xbox they may favour it with more exclusives (or at least release the Xbox version first).
All theory of course, but as someone who only uses a console to play games and has little time to do anything that would require more freedom than the Xbox allows the practical differences between the Xbox One and PS4 are negligible and other factors are likely to take greater sway.
I think this will be an interesting test. With the consoles releasing more or less side by side and with similar capabilities it will perhaps help show once and for all whether DRM can be done in a way that makes customers prefer it.