In my case, I'm severely restricted in what I can carry in my urban kit. It needs to be light, fit in a couple of pockets of my laptop bag, and it needs to conform to Corporate Correctness.

My urban kit has much less emphasis on fire. Shelter is somewhat reduced -- I do have a little cordage and a two-person Heatsheets. There's exactly nothing in the Signalling area unless you count my cellphone (including two standalone ways to charge it) and the shiny side of a CD-ROM. Same for navigation (I know the area extremely well and I should have no problems using commuter rail, car or shank's mare to get wherever I might need to go without navigation aids). First aid kit and folding knife are both smaller, and I don't carry a fixed-blade knife. While I carry water I'm likely to have more of it in my hiking kit.

My urban kit does include a small AM/FM/shortwave receiver, whereas my hiking kit will include my amateur radio HT (which receives everything that the receiver in the urban kit does and a bunch more). I also make sure to carry at least enough cash for a cab ride home.