Red Viper dying leads for more interesting consequences than the Mountain winning. I'm sure Dorne will be none too pleased one of their princes died. So at the very minimum it will strain an already strained relationship between Lannister and Dorne. Possibly all out war. I feel Tyrion is basically untouchable and really doubt he'll die. I know that is a silly feeling for this show but I feel he, Arya and Sansa aren't going anywhere soon. So something will have to happen to get him to escape an axe to the neck.
If the Mountain died he'd just be dead and Tyrion free with Cersei at maximum rustle. That isn't nearly as interesting.
If the Mountain died he'd just be dead and Tyrion free with Cersei at maximum rustle. That isn't nearly as interesting.