I've used both, and plenty of other tools. I really think these types of tools need to be aligned with the type of team you have and the workflow you plan to use. There are a dozen tools that will fit the bill on a feature breakdown. With real-world use, with your team, with your project, with your environment, you'll discover a clear winner.

Some notes on products I've used, for reference:

FogBugz: A few years ago it was reasonably lightweight and decent. It's gotten more complicated over the years and I couldn't stand it the last time I checked it out.

JIRA: The "enterprise" solution. Infinitely flexible, with all the positive and negative aspects that go along with that. Best API of all of them, though, IMHO.

Pivotal Tracker: I've used Pivotal several times over the years, and to be honest the UI is very cumbersome to use IMHO, and the density of features make it fairly heavyweight to use.

AgileZen: My personal all-time favorite for managing development projects. Fits a kanban-inspired mould, which I tend to like quite a bit. JIRA offers a kanban-board view as well, BTW.

If I were you, I'd sign up for free accounts for all of these and use them for a week or so. It's the best way to find out if you like how the tool operates and if your team will actually use it, which is more important than any specific feature.

I'd also take a second look at your requirements. I wouldn't discount a SaaS tool for no reason. SCM integration (svn, git) can sound nice, but to be honest I've found that it adds too much friction to the commit workflow (to add a story ID or whatever) and is usually of little value).

I just spent a couple weeks comparing Jira, Bugzilla, Fogbugz, and Redmine. I'm at multi-faceted design group doing firmware, desktop software, and silicon design(multiple codebases / documentation), and I wanted a system that will work for everyone, and let me move issues across projects to their root cause. I also wanted it to have email-in support to make sure employees have no excuse to not file an issue.

Fogbugz: likely my favorite from a user-interface standpoint. But I needed project categories, something you can now write a plugin for, but didn't have time to deal with. Their Kiln product looks great, but you may need to check if it's svn/git compatible -- I think it's primarily mercurial.

Redmine: I would've chose this if it was a small group. It's free, open source, lets you create compartmentalize into subprojects probably more than you should. But I had fears of ruby scaling out to a bunch of people. There were also some UI quirks that bugged me (e.g. global search should always be enabled, even in a project), although there's some gorgeous themes coming out for redmine soon.

JIRA: What I ultimately chose. It's definately a "wine of fear", that is an enterprise product with many features thrown in not to offend or lose business. Because of this, you get a fairly boring UI, and can feel bizarrely complex to configure. That said, it works.

At my last company, we used FogBugz for almost two years but started exploring other systems the last few months I was there.

I initially chose FogBugz because I loved how easy it was to create a new issue in the system (which at the time was significantly better than the others I tried). It only requires a single line of text for the description. There are additional fields you can use, but they are never required. That said, FogBugz's UI hasn't quite kept up with the latest and greatest, so we found it to be somewhat unsatisfying and even quite annoying at times (not enough inline editing for example). Ultimately the reason we started exploring other tools was because of its slow performance (although I'm not sure if it was due to having it deployed on a Linux server rather than Windows).

We tested Jira with the GreenHopper plugin (agile development) for about a month. Most of the team made the transition quite easily (a few guys wanted to go back to FogBugz) and it was significantly faster than our FogBugz system--which made the team much happier. For our planning meetings, we all really liked the user story board view in GreenHopper, and overall I found the user interface more usable than I expected. However, Jira definitely feels like a typical old-school 'enterprisey' Java app that has been quickly updated to stay current (not to mention the sprawling feature set it has accumulated over the years). Its UI definitely lacks the cohesiveness of FogBugz (and especially Pivotal Tracker).

In the end, our company was acquired by a company also using FogBugz, so the team never had a chance to make a decision one way or the other.

Have you tried/looked into Redmine (http://www.redmine.org/)? I've heard it's quite good.

Redmine's got a ton of core functionality. Wiki, forum, repository browser, sub-projects, gantt charts-- a lot. Simple, straightforward interface with occasional quirks.

I've found the plugins to be mostly non-functional. Figured I could quickly mash together a CRM and real-time chat, but, alas this was not the case.

we are using redmine as well. It's good system

I don't like either. Whiteboard please!