When you are talking about the best performance, can you, please, clarify what parameters or properties can you achieve or improve and what is your the main goal of your photonic crystals application? For example, if you are investigating birefringent properties (for such devices couplers, splitters, polarization rotators, etc.) then the crystals with biggest asymmetry should work much better. In other case, you will not need these properties, i.e. for waveguides.