Do you have the PDF rules for Orcs? They're available on the
GW website and that would surely help the decision.
http://www.games-workshop.com/en-CA/Warhammer-Age-of-Sigmar-Rules
Not familiar with the model and its options myself but looking at the PDF, the big axe gets half the attacks of the pair of choppas but does a lot more damage per hit. I think there's a case for going for a pair of choppas because of all the attacks, but I like rend and damage. His command ability to frenzy units around him is very powerful.
The banner is pretty nice too, giving re-rolls for wound rolls of 1 for everyone within 16 inches. Pairs well with the command ability, which you can still get with the banner. He's almost useless in combat though.
I don't think you can really go wrong but it looks from the war scroll to me like a decision between the extra area buff the banner gives and the more powerful combat ability going with the axes or one big axes would give.
From my reading of the Start Collecting boss, it looks like you get options to build both, so I'd say you can't go wrong making one a banner guy and one the more fighty one.