A cargo bike for touring is like welding a bike trailer to your regular bike. You might appreciate it when on a long tour, but in all other cases it's a ballast you can't remove. The difference with a trailer is that you can take it off when not needed.
And this is coming from someone who is currently desperately trying to justify the purchase of a bike quite similar to a cargo bike. The truth is that a trailer gets you there for MUCH less money and more flexibility.