Welcome to the pain boards. Vicodin is considered to be stronger than tramadol, although tramadol might be the more effective pain killer dose to dose, I'm not sure.
They are very different meds. Vicodin and Percocet (Hydrocodone and Oxycodone, respectively) are very similer in how they work and how they make you feel, but Tramadol is a synthetic opiate that also contains a seratonin reuptake inhibitor, similar to prozac, and while its pain killing properties may be equal to, the actual medication feels completely different than a traditional opiate med.
Would it be possible for you to let us know a little more about why you want the info? are you new to chronic pain, whats your diagnosis, if any, just a little bit helps the right people respond to your posts, people who have shared your issues or been on the same meds, ect.
Anyway, welcome to the pain boards!