I don't think argument are necessarily worse in a poly family. You have more people involved, but that can also mean more support, and more points of views to try and see the situation clearly.
I don't see arguments as a match or something like that, for me it means there is a problem and you need to get together and solve it. Sometimes it will take some one by one discussions, sometimes a talk all together.
I haven't had an argument yet with my husband and boyfriend at the same time but I have found that during a hiccough with one of the two, the other was essential support for me to get better.
This being said, I am a pivot, so they're not involved with each other (although they really get along and look out for each other) and your case might be different.