Actually I am confused with the working of these tools.
Both mentioned products are defect trackers, probably with their own style and workflow.
Kanban is a visual process management system, both tools have a Kanban plugin:
I would expect both products to deliver similar features with respect to defect tracking and planning with the Kanban plugin. If you want to know which one to choose, install both and see if your requirements fit.
The difference: between a defect-tracker and Kanban is that one is a tool to manage defects, the other is to manage a process workflow. The development workflow would include fixing defects, but also requirements and maybe other tasks. A defect tracker is a just a list with known defects (and details like how to reproduce) and their state, open, closed, etc...
Also read: A brief introduction to kanban
As Niels said, Kanban serves a process management by visualization, while bug tracker is meant to track specific aspects of a certain, not-visualized process. I think, that this does not necessarily mean that one cannot use kanban for bug tracking, does it? Reason I think so is, because I do it. I'm a kanban tool user, and have a couple of different boards. One for general process management, one for bug tracking, one for maintenance work. Works great for all instances. Kanban is just very flexible. Hope this is of help also.