So I think both 14...Nb4 and 14...Nxc3 have some merit here.
14...Nb4 posses a lot of threats such as 15...Nc2+ or 15...Nd3+ and the least I hope to gain from this is a monster knight on d4
14...Nxc3 also seems fine. I don't win any material immediately but it seems like I will eventually win the c3 pawn and from what I can tell the resulting endgames appear to only have black able to play for a win which is great.
I am very tempted to threaten with 14...Nb4 but I think I'm more comfortable with less pieces on the board.