Wait what? I've used both and I can't see anything good about Fogbugz over JIRA?
JIRA is awful. But fogbugz? fogbugz? It's the worst piece of crap I've ever used.
What do you use then?
Both, unfortunately. But if given the choice, I'd go with JIRA, simply because I know
of no better solution. To clarify, maybe there are better tools, but it's not my job
to assess all the PM tools out there.