The problem is the people who make the decisions are rarely the people who pay the price for bad decisions. I've worked with many vendors who promise integration will be straightforward and that their software is easy to extend to handle the last 10% of our business flow that it doesn't currently cover.
In truth its usually a huge pain and time sink and it's the developers (on both sides) who end up working crazy stressful hours to get the project finished.
How can you expect the developers to go the extra mile and fix your dumbass decisions when you didn't listen to them in the first place?
Sometimes everyone has to pull on the same side of the rope.
I'm not specifying (and don't believe) that democracy is the best way to resolve a technical debate, but I am saying that once a path is decided, however decided, you pull in that direction or you need to be removed.
I'm in the Netherlands, where hierarchy is a bit of a dirty word, and educated employees are all expected to be critical, independent, outspoken thinkers all working towards a common goal. That has many advantages, but the technical discussions about pretty small details can go on forever...
If above is not enough to get an agreement, let the two people work it out on their own with a limit on how much time they can spend on it (and really limit this time). No need to have an entire team listen in or extend an existing meeting for ages (meetings should be brief).
Aside from that, sometimes you just need to do. So something like "it's not a perfect decision, but what you're saying is known and now it is time to do".
I'm from the Netherlands btw, though 50% of my colleagues are foreign.
Once a decision is made, it becomes everyone involved in the implementation's job to make it successful. If someone is openly running counter to that and isn't corrected or removed (at least from the project, and possibly from the company), you have a basic and straightforward leadership problem, IMO.
(In the second case of inter-company alliances, that's more normal and less amenable to a simple solution. It's also far less cancerous if left unchecked.)