I've been in both kinds of relationship so hope I can provide a helpful view.
We don't ever have rows of the shouting, getting angry type, I don't know if this is a "healthy relationship" thing or just our respective personalities, but we do of course have disagreements.
The first difference is that we can bring it up without the other person feeling like it's an attack on them, so no defensiveness, just openness and concern for what the other person has to say. If it does happen to be something that, e.g. I feel a bit sensitive about, I might feel a bit wobbly and have a little cry. DP always feels bad if this happens
. We talk about it, he reassures me that he doesn't want to break up with me, I admit the reason I am so upset about it is because I'm aware it's a problem and we work out a plan together going forward for it to get better, which isn't just me changing things but usually both of us - am just reading this back thinking it sounds really one sided but DP tends to be more "together" whereas I am more emotional and obviously I'm giving you my view - his would probably be different. The crux of it is that we don't just discuss/argue and leave it with bad feeling and nothing solved, we work together to see if we can find a way through it or a compromise that works and then we do it.
This is a really rare occurence, as well - we've been together almost 3 years and I think we've ended up having a talk like this about four times ever.
Normal disagreements about things like where to put stuff, what kind of sofa to buy, we just discuss it with our various reasons/arguments and mutually agree on the best thing.
We don't argue about big topics like how often one person is allowed to go out, drugs/alcohol/smoking, child rearing technique etc because we have similar (or compatible) moral values so we both feel that the same sort of thing is acceptable. This was sort of an accident, so we were lucky, but I really think this is of utmost importance in a relationship now. I don't think you can get past arguments which start as a result of a differing moral view about something.
Also we both support each other and put in what we can, taking what we need, so we don't tend to argue on topics of "You haven't done XYZ" although we sometimes ask the other to do something specific.
Sorry that took me ages to write so probably will have xposted with loads.