From an optimization standpoint, Hexblades are good for one of two things.
1. A three level dip for Arcane Resistance and Mettle.
2. Single classed ONLY far enough to get an Improved Familiar (Worg) and create a mounted charging character.
Therefore, you need to look at what you want the PC to do. If you want a single classed Hexblade, then you'll probably want a mounted, mobile charger that rides a hardcore combat familiar and plays as a frontline fighter. In this case, any race that provides a decent "Fighter" race will work.
In all honesty, just choose a race that doesn't take a penalty to Con or Str and you should be fine.