There are little differences between the Bug-zilla and RT. The main ones, AFAIK, are that Bug-zilla does not have an email-based interface to update / create requests, and RT have a nice interface for this.
Also, RT offers an interface to customization and the possibility of maintaining multiple queues (for lines or families of products, for example) and Bugzilla keeps an individual bug list.
As a final consideration, Bugzilla and RT have different bug-management paradigms: Bugzilla uses "there is no bug without an owner" and RT uses "There are Requests, even if there is no person to solve them". I think RT's approach is more generic, what is a Good Thing(TM).
In your place, I would start with RT and, if I found that this is more than I need to solve the bug-tracking problem, I would switch to Bugzilla (or any other).