I think Replicate is the generally stronger ability, but it's mostly on crap champions in factions that can't take advantage of it, whereas Split is on a lot of good units (and is also cheaper, which makes it less subject to being on the right champ in the first place). Edit: And, reviewing the two abilities, several of the champs with Replicate have Healing Deficiency specifically to prevent the ability from being good.
i am asking because i am using a sp/ud beast deck with magma bunny. I like the rune but don't know if i should keep replicate or split
Well if I go leap 3 and split, magma bunny is 56 Nora. I can get a duo spawn with one of my other runes and start font contesting earyler (my plan).