Rock vs Cena.
Cena unfortunately wins because Rock "coming back" is only temporary. This sucks because Cena is a giant tool. Even if he turns heel he's still a tool. He will always be a tool, and he just needs to jump off a cliff to be quite honest. But little kids love him and he's the poster child for the PG era of WWE/Raw.
Undertake vs. CM Punk
I just don't think the WWE will tarnish a record on one of their greatest stars ever, one that put the company on the map, for someone that no one will know/remember in 20 yrs. CM Punk isn't a larger than life star, in fact no one really is except "maybe" Cena and only because he's been used over and over again as the company's poster child.
2015 Adopt-A-Chief: Derrick Johnson #56