Well broken blade is great for damage. Note Strikes gives you +2 to damage rolls with discipline weapons, and plenty of BB has multiple attack strikes.
Silver Crane has great versatility with Healing and Protection for the party, and if you are going into a campaign with evil outsiders and or undead it is really strong all around.
Steel Serpent is kind of odd. It offers great sneaky options and grappling options as well as ability damage, but as a Unarmed character Im not sure you can benefit to much from the poison options. Probably the easiest one to shut down overall as well.
Of course, you can always pick up all 3 by using the
Warpath Follower Martial Class Template. It isn't compatible with Sacred Fist, but will save you 6 feats and give you more options, and most of the stuff from Sacred Fist that is lost can be covered with a few feats or a dip into Monk.