I present my arguments as simply as possible, and try and compare the system's features to what my friend wants to get out of it. I mean, a LOT of people like to use their "gaming" console as more of a Netflix/Hulu/Youtube/Amazon video box. Nothing wrong with that, and from the presentations so far, the Xbox One might take the edge on the extra features. Of course Halo is a big reason my friends own the 360, and that will be a big motivator for most to get the One as well.
But honestly, this is going to be a tough sell to my few cash-strapped hardcore gamer friends. The PS4 is still cheaper, and did have a lot of 'wow" factor at E3 aimed at the gamers. To those friends, I wouldn't necessarily tell them not to get the PS4, but to consider waiting for the first price drop on the Xbox One.