I think the only valid distinction here is, is the MLC affair one in a SERIES of addictions, and did it happen after some specific, traumatic life event? Cuz other than that, I just don't see much difference in the presented behaviors.
Puppy
I suspect that, once it's begun, one affair is much like another. The difference is that the affair is only one part of a recognizable series of stages that the MLCer goes through, and not the final one. Some MLCers don't include affairs among their addictions. Somewhere in the resources I read that even nuns & priests can have MLCs, even without spouses to react against.
One of the earliest MLC feelings my H later described was a desperate urge to run away. Jim Conroy similarly talks in his book about being overwhelmed by an intense desire to bolt to a desert island. The MLC journey to find inner healing involves a lot more than the affair--however, it's the affair which catches the most attention.
