The components of dialogue are: thesis + antithesis = synthesis. Arguments are worthwhile (feel like "winning") to me when they successfully yield some synthesis. Or as Jung put it, "The meeting of two personalities is like the contact of two chemical substances; if there is any reaction, both are transformed." But where one or both people have some preconceived notion of what ‘synthesis’ the other person should walk away with- where one person expects to 'transform' the other without being affected themselves- that’s not especially satisfying to me (even when I’m the one who falls into the trap of being antidialogical- it invariably feels bad afterwards).
eta: Although really- I guess I don't think both ends need to be 'transformed' for some idea/concept to be a 'winning argument', I just need to feel like some transformation has taken place. Because I can read something I'll consider a 'winning argument'- and it will still be a 'winning argument' to me, even though the writer hasn't been 'transformed' by the fact that I've read it. I guess I need for there to be an authentic transformation of POV (be it mine or someone else's) to take place to consider something a 'winning argument'- coercing someone else to agree or adopt a foreign POV through aggressive tactics is what I'd consider inauthentic transformation, and that's not 'winning' imo.