(I was going to give your team a shout-out if you hadn't beat me to it!)
As a more specialized project, you'd expect IPFS to be better at the part of the problem it solves, for the same reason a sprinter sprints faster than a decathlete. (Not to mention that JB is awesome.) On the other hand, not having an identity model other than public keys (or, to put it differently, not trying to square Zooko's triangle), imposes certain problems on IPFS that urbit doesn't have. For instance, with routable identities, you don't need a DHT, and so the idea of a hash-addressed namespace is less interesting.
That said, it would be easy to imagine a world in which urbit either could talk to IPFS, or even layered its own filesystem (which has a fairly ordinary git structure under the hood) over IPFS. Like I said, it's a cool project.