It does not matter who files first unless it goes to trial (very, very, rare) and then the only thing that matters at a trial is the person who filed first has to take the stand first. No biggie. Attorneys will try to get you to believe it make a difference just to get the case going but it does not.

I went through mediation, of course to me now it seem like the worse thing ever, but my EX was the one that filed. I got what I thought was fair at the time and reasonable I guess. I only good thing is he no longer lives here even though he seems to think he does.

Outcome is the same. If his attorney is doing more of the work, he has more of the expense.