I concede. Opera is better than Firefox in many ways, though I still prefer Firefox :P
One of these is the way non-ascii URIs are handled in the location bar. Goto http://hi.wikipedia.org - You location bar will look something like this:
Lets look at how Opera renders it.
Better innit? Lets look at the Japanese wikipedia...
This said, both display the actual article in the exact same way, and the problem is probably linked to bug #150376 in Mozilla Firefox. Not assigned to anyone, but it'll probably be fixed soon.