Well? Who would win? It's difficult, because while a Mistborn is more agile and quick (most of the time ), a Radiant would have a shardblade/honorblade. And, it would depend on how much Stormlight/Metals they had. Also, if the mistborn had any of the temporal metals, that would give another advantage. Also (if the Radiant had enough Stormlight), the Radiant could heal themselves.
So, what do you think?