It's an interesting question, and actually, I've seen setups like this in my job, for example, I've seen one company use a Cisco ASA and then right behind it a Checkpoint firewall, and to be honest I can see the method to the madness.
However, considering a lot of firewalls issues are actually caused by a misconfiguration as stated in your post, so realistically, I don't see it making a massive impact.
When vulnerabilities are found in firewalls (and other products) most of the time they're rectified by the product security response teams very quickly, and usually all that's required is putting a new version of firmware on the device. The faster you carry out this upgrade the better. In general, I don't see this making a huge difference, if your firewall is proactively maintained and security threats are responded to quickly, I am not sure spending extra money and resources on maintaining two different firewalls is all that worth it.
In the end, it comes down to your threat model and your budget, I would say if you are protecting something really valuable, two different firewalls from different vendors is potentially beneficial - in the end, it is quite hard to answer this question as it does, in reality, come down to your threat model.