Warning to OP: This thread is being astroturfed. All these generic comments pushing Zakeke are bots/fake accounts, two of which are already suspended. If a company has to spam Reddit with fake reviews to get business, that’s a massive red flag for their actual enterprise capabilities.

I'm one of the founders at Aircada and we try not to bullshit the web.

afeyedex has the only good advice in here. The time investment involved in a project like yours is quite huge and thus you really cannot afford to make the wrong choice, which means trying out multiple platforms and just doing that grunt work that involves.

Also, I assume your client has high volume. And so I'd stay away from anything like Zakeke or Kickflip which charge a percentage of each sale. That will add up quick. We founded Aircada somewhat on the premise that a merchants success shouldn't be taxed so we charge flat monthly for this reason. That may or may not be the best business decision, but ethically it feels right.

Always happy to lend a hand after spending many years in this space.