Glory

The job is exciting; you get to try some pretty big cases right away and are given a lot of autonomy. A junior associate in a law firm wouldn't get that kind of treatment.

Even better, you can grandstand all you want (as long as you win), just like Al Pacino in "And Justice For All."

And who knows—if you play your cards right, you could end up someday as Attorney General. (Source)

It also looks great for your résumé to be an AUSA. It will lead to bigger, better, and more lucrative offers with private firms as a trial lawyer, once you are seasoned and sizzling. That'll feel pretty good...eventually.

For the most part, the glory in this position will come from knowing that you are doing the country a service. You'll help put away some of the biggest baddies possible.