Honestly in this situation something quick sounds best, a quick exchange of boasts and then fighting until one of the champions falls, submits, or begins bleeding is probably enough.

In other situations duels might be more complex, lethal, or just plain different. Yes some variety of 'the one remaining in the arena is classic, but you haven't experienced life until you've survived an orcish poetry duel (they tend to last nine hours and orcs have a *lot* of terms for sex). You can theoretically duel via anything that can be made competitive, especially if you're able to have an unbiased set of judges. Be different, give your orcs traditions not related to hunting and killing!