I'd enjoy Cena/Taker more than Brock/Taker because:
-The heat and drama surrounding the match thinking Cena might actually break the streak. There's no doubt that Lesnar would lose to Taker. Not that I'm complaining, sometimes things are predictable and still awesome, just saying. (I've no problem with Taker/Lesnar happening, for the record, Taker/Cena can always wait to next year.)
-It would have the build of Cena saying he's defeated everyone else and accomplished everything else, and he now feels it is fated for him to defeat the streak as the pinnacle of everything he's ever accomplished. This should make people dread the thought of Cena winning and make them side with Taker more than ever.
-Imagine how much people will be on the edge of their seats more than ever before when you get to the near falls late in the match and Cena starts hitting those AAs on Taker. Some people will probably be on the verge of a heart attack lol.
-Cena is the perfect opponent for Taker to retire on (in the event that he's retiring undefeated, as I expect him to.)