Both are very impressive. Without them fighting 100 times there is no way to tell which is more impressive, which is a fluke, which fighter is more likely to win, etc... just too small a data sample.
Agreed. Anything can happen in a fight. You have to erase the memories of previous fights, in some sense, as it is a brand new fight and fighters have improved since their previous meetings.
The rematch and the way Cain dominated JDS kinda makes the first fight look like a fluke.