Let's not start making boastful claims where we have not done our research yet. Let's not get our feathers ruffled up over such a topic as the Balrog vs. The Witch-King. (Maybe if it was over Balrog wing's that would be a little more understandable
).
This is a
'what if scenario,' and also a
'someone-or-another vs different someone-or-another'. Which this means no offense, but threads such as this are not ones that too many people are going to take intellectually.
To pose a what if, since this is a 'what if'...well what if the Balrog leaves his dirty underwear lying all over the place?
How is the Wiki going to feel about that? There's nothing to get flustered about.
I think the question you've posed is pretty clear and has already been answered. But if it hasn't...Durin's Bane proved to be even a mental strain upon Gandalf. Durin's Bane wasn't just physically strong, but he wore Gandalf out even before their big confrontation at the bridge. So, hands down, whether it's a bout, or some sort of psychological sparring, Durin's Bane would win. The Witch-King's primary weapon is fear (that is a 'psychological weapon'). Why would Durin's Bane have a need to fear the Witch-King? He didn't fear Gandalf? He didn't fear the dwarven kings he slew? If Durin's Bane didn't fear the Wiki, the Wiki was pretty much useless (just as he proved to be useless to the likes of Glorfindel and Gandalf...etc because they did not fear him).