Danks has a better track record and is the safer of the two starters, but E-Jax has shown the capability to be the stronger of the two (and I think he has more room for a rebound this year). With that said, I'd feel safer with Danks on my roster.
I am not a Reynolds fan (I don't know what it's like to own him in a league that doesn't directly factor in strikeouts against a player's value), but I am still not so sure about what you gain in return for parting with him. If I'm reading the roster correctly, you have 3 slots for potential closers, and all are currently filled. Gregg is shaky, but it seems as if Francisco isn't that much of a better bet. You'd build a nice little bit of depth there with the four save sources, but how much is marginal closer's depth worth anyway?
I don't know. Overall, I don't think I'd want to lose Danks for those particular returns.
if you can get reynolds for FF that's obviously preferably since danks is a zillion times better than ejax (slow start notwithstanding). that being said, mark reynolds is totally un-ownable so getting a closer for him is a pretty good deal. i'd pull the trigger if i had to but try not to give up danks.