Difficult question. Small individuals will molt more frequently and therefore are subject to more problems associated with molting. On the other hand, if you have a good system and the animal is living in a "natural setting", the small animal certainly will have the potential of living longer. Practically, I have better luck with large O. scyllarus, but some other gonodactylids such as N. bredini, G. mutatus, G. chiragra and P. ciliata do well when collected small.
Roy